EIGRP Authentication

An EIGRP enabled router may have authentication configured. This authentication should be the same on two routers for them to form adjacency

An EIGRP enabled router may have more than one key for authentication. This is for automated reason. So, if for example that later you decide it’s time to change the password for EIGRP authentication, you don’t have to configure all EIGRP routers all at the same time so they have the same key for authentication.

Keys in EIGRP can be given the start and end valid date. Usually you will give a short amount of time (an hour to a day) that the old key and the new key can be used (two keys are valid at a time). Say that at Dec 1st 2010, your old key will be expired and you choose a new key that will be valid at Nov 30th 2010, so that will give an error buffer, if for some reason there are some error preventing some EIGRP routers to communicate with each other.

To configure authentication in EIGRP, first you must create a key chain. In global configuration mode.

key chain WORD

WORD: the name of the keychain. Example key chain EIGRPAuth

After entering the above command, you will be inside the key-chain configuration level. Here, you can specify some keys as you like. The command is

key NUMBER

NUMBER: a number value, this is just for an identification for each key.

After you enter that command you will be in the key level configuration level. Here, you specify the string of the key (like the actual password of the key) and the send-lifetime and the accept-lifetime. Send-lifetime specifies the time when this router will send that key for authentication, the accept lifetime specifies the time when this router will be accepting that key.

The commands are

key-string WORD

accept-lifetime HH:MM:SS MONTH DATE YEAR HH:MM:SS MONTH DATE YEAR

send-lifetime HH:MM:SS MONTH DATE YEAR HH:MM:SS MONTH DATE YEAR

the first part of HH:MM:SS MONTH DATE YEAR is the start time while the second part is the end time.

A complete key chain configuration example as can be seen in a running-configuration is:

key chain EIGRPAuth
key 1
key-string student
accept-lifetime 12:00:00 Jan 1 2010 12:00:00 Jan 2 2011
send-lifetime 12:00:00 Jan 1 2010 12:00:00 Jan 2 2011
key 2
key-string cisco
accept-lifetime 12:00:00 Jan 1 2010 12:00:00 Jan 2 2011
send-lifetime 12:00:00 Jan 1 2010 12:00:00 Jan 2 2011

you must create these key chain configuration on other EIGRP routers too. To avoid setting wrong lifetime of the keys and end up with a chaos because of the different keys, you can just copy and paste this from the running-configuration and paste them on other routers.

After making those key chain, you enable the authentication per-interface basis. The commands are

ip authentication mode eigrp AS-NUMBER md5

this command turn on eigrp authentication on the interface. there’s only one mode available, which is md5 (don’t know why this command exists if there’s only one mode available).

Next step is to specify which key chain to be used for authentication. The command is

ip authentication key-chain eigrp AS-NUMBER WORD

WORD: the name of the key chain.

You must configure authentication on both routers, if one is not using authentication, the neighbor adjacency will down.

The key used to send is the first valid key sorted by the key ID. If key 1 is no longer valid to be sent, key 2 will be used instead.

Routers will receive keys based on the key id not the key string. The key ID sent should match the key ID set on the peer router.

OSPF Packet Types

There are five types of OSPF packet types. The following figure describe the different types of OSPF

1. Hello - Hello packets are used to establish and maintain adjacency with other OSPF routers. The hello protocol is discussed in detail in the next topic.



2. DBD - The Database Description (DBD) packet contains an abbreviated list of the sending router's link-state database and is used by receiving routers to check against the local link-state database.



3. LSR - Receiving routers can then request more information about any entry in the DBD by sending a Link-State Request (LSR).



4. LSU - Link-State Update (LSU) packets are used to reply to LSRs as well as to announce new information. LSUs contain seven different types of Link-State Advertisements (LSAs).



5. LSAck - When an LSU is received, the router sends a Link-State Acknowledgement (LSAck) to confirm receipt of the LSU.

OSPF packet Type 1 is the OSPF Hello packet. Hello packets are used to:

• Discover OSPF neighbors and establish neighbor adjacencies.


• Advertise parameters on which two routers must agree to become neighbors.


• Elect the Designated Router (DR) and Backup Designated Router (BDR) on multiaccess networks like Ethernet and Frame Relay.

RIPng

RIPNg Routing Protocol
RFC 2080 defines Routing Information Protocol next generation (RIPng) as a simple routing protocol based on RIP (based on RIPv2. has the same features such as, a distance vector routing protocol, max of 15 hops, split horizon and poison reverse). RIPng is no more less and powerfull than RIP, it supports IPv6 network without having to build a new routing protocol.
RIPng has the following features:

• Based on RIPv2 and is similar to it
  
• Uses IPv6 to transport
  
• Includes IPv6 prefix and next-hop IPv6 address
  
• uses the multicast group FFo2::9 address (IPv6 multicast address identifying all RIPng routers on link) to send updates. this is similar to broadcast function in RIP.
  
• sends updates on UDP port 521
  

RIPng is supported by Cisco IOS Release 12.2.(2)T and later. in dual-stacked deployments, both RIP and RIPng are required.

Configuring IPv6 addresses
first we must enable IPv6 traffic-forwarding in Cisco router (by default this feature is disabled) by entering the command "ipv6 unicast-routing" at the global configuration level. then you can configure the address of the interface by using the manual configuration or the eui-64 standard (see above).

• - manual interface ID assignment. one way to statically define the IPv6 address for a device is to manually configure both the network (prefix) and the interface ID to the device. to assign an IPv6 address to an interface in Cisco router, enter the following command in the interface configuration level
  

ipv6 address ipv6-address/prefix-length

ipv6-address: the address of the interface in IPv6 notation, example 2001:A58E:9CD:2947::49
prefix-length: the length of the prefix (network) portion. example /64

• EUI-64 interface ID assignment. EUI-64 standard define the way to stretch the MAC address, which is 48 bits, of the interface to a 64 bits interface ID used for IPv6. the convertion is done by inserting the 4 hexadecimal values of "FFFE" at the 24th bit of the MAC address. example, a MAC address of 00:0c:4F:90:27:FC is converted to 00:0c:4F:FF:FE:90:27:FC. to assign an IPv6 with the EUI-64 scheme to an interface in Cisco router. enter the following command at the interface configuration level.
  

ipv6 address ipv6-prefix/prefix-length eui-64

ipv6-prefix: the network (prefix) portion of the address
prefix-length: the length of the prefix (network) portion

example,

ipv6 address 2001:A58E:9CD:2947::/64 eui-64

Cisco IOS IPv6 Name Resolution
two ways to perform name resolution in Cisco IOS

• Statically define a name for an IPv6 address. use the following command at global configuration level
  

ipv6 host name [port] ipv6addr [{ipv6addr}..]

name : name of the ipv6addr
port : telnet port to be used for the associated host
ipv6addr: the address of the hostname. there can be up to four addresses for a given hostname

example,

ipv6 host router1 2001:A58E:9CD:2947::1

• Define a DNS server to query. the hostname database is not located at local router but at a particular server. use the following command at the global configuration level
  

ip name-server address

address: the address of the server

example,

ip name-server 2001:A58E:9CD:2947::1

Configuring RIPng
first use the command "ipv6 unicast-routing" to enable IPv6 traffic-forwarding. then create a RIPng process by using the command

ipv6 router rip name

name: name/identifier of the RIPng process

the command is to be entered at global configuration level. next, give each interface required to join in RIPng an IPv6 address. after that, instead of using the "network" command to make a particular interface participate in RIP process, RIPng use the command

ipv6 rip name enable

name: name of the RIPng process that the interface to be participate in

enter the command at the interface configuration level (at the interface required to participate in RIPng). the name must match with the name in the "ipv6 router rip" command. enabling RIP on an interface dynamically creates a "router rip" process if necessary.


example,
enable RIPng on a Cisco router named RIP1. give FastEthernet0/0 an IPv6 address of 2001:9cd:1:3::10, and FastEthernet0/1 an address of 2001:9cd:1:2::10 make inteface FastEthernet0/0 and FastEthernet0/1 participate in the RIP1 process. the commands are

ipv6 unicast-routing
ipv6 router rip RIP1

interface FastEthernet0/0
ipv6 address 2001:9cd:1:3::10/64 eui-64
ipv6 rip RIP1 enable

interface FastEthernet0/1
ipv6 address 2001:9cd:1:2::10/64 eui-64
ipv6 rip RIP1 enable

instead of using "show ip" command, you can use the "show ipv6" (there will be some next command options such as "show ipv6 route", "show ipv6 interface" and "show ipv6 traffic", try the "?") to see the configuration related to ipv6.

EIGRP

EIGRP is ac Cisco-propietary routing protocol, so only Cisco routers can operate this protocol. Junpier / Nortel wouldn't be able to communicate with your Cisco routers using this protocol

EIGRP is easy to use and manage, but always calculates everything because it's also the main reason of mibehaving networks using EIGRP.

EIGRP is called a hybrid protocol because it combines the feature of distant-vector protocol and link-state protocol.

EIGRP advertisement will only be advertised to the same router running EIGRP in the same autonomous system. in a cisco router when you enter the eigrp configuration, you alse specify the autonomous system number (ASN). example

router eigrp 100

this will be enter the configuration of eigrp for asn 100

EIGRP use classless routing.
EIGRP is an enhanced of IGRP (IGRP is also cisco propietary).

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EIGRP's value
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Hello time - most network 5 secs, NBMA 60 secs
Hold time - default three times hello time (15 / 180)

hold time = time before a router assume that the end router is down because it's not receiving hello packets anymore.

both use metrics composed of bandwidth, delay, reliability and load. both routing protocols use only bandwidth and delay.

Cisco discontinued IGRP starting with IOS 12.2(13)T and 12.2(R1s4)S.

EIGRP doesn't send periodic update and route entries do not age out. periodic packets that are send between EIGRP neighbor routers are lightweight hello. this is used to monitor the link between routers, updates are sent when changes occur (link added, or become unavailable)

EIGRP doesn't use holddown timer.
communication between EIGRP routers are sent through multicast 224.0.0.10 address.

DUAL (Diffused Update Algorithm) is the algorithm used by EIGRP. with DUAL EIGRP doesn't use hold-down timer and split horizon primarily for routing loop avoidance. EIGRP primarily use DUAL to avoid routing loop, EIGRP maintains a topology table beside the routing table. this topology table maintain the best route to a destination and any loop-free (loop-free mean that neighbor router doesn't have route for the destination network that pass through this router) backup routes. when a route become unavailable DUAL will see if any backup paths exist and enter it to the routing table.

EIGRP support routing for other layer 3 technologies beside IP, such as IPX and AppleTalk. for each of the techonology, EIGRP maintains different table. so each technology has its own topology table, routing table and neighboor table. because of this, EIGRP doesn't use TCP/UDP as its layer 4, because IPX and AppleTalk doesn't support TCP/UDP. EIGRP uses Reliable Transport Protocl (RTP). even its name is reliable, RTP can work as a reliable or unreliable

Although EIGRP refers to the parameter as an "autonomous-system" number, it actually functions as a process ID. This number is not associated with an autonomous system number discussed previously and can be assigned any 16-bit value.

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Metric calculation
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EIGRP can use Bandwidth, Delay, Reliability and Load to calculate the metric. by default only Bandwidth and delay are used for metric calculation. each factor has its own weight. each weight is presented as K1, .. K5. k's default value

K1 (bandwidth) = 1
K2 (load) = 0
K3 (delay) = 1
K4 (reliability) = 0
K5 (reliability) = 0

you can see these values on a router by entering the "show ip protocols" command.

K is the value of the metric weight, by assigning different weigh to k you can set the metric calculation to be weighed to what factor. to see the actual value used for metric calculation by entering the "show interface" command. you may see a lot information but take a look at the section similar to the following:

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255
(note MTU is not used for metric calculation)

Bandwidth - is a static value. the value of the bandwidth may or may not reflect the correct value of the physical bandwidth of the interface. the value of bandwidth in an interface can be changed. bandwidth is measured in Kbit. in most serial interfaces the default value is 1544 Kbit.

Delay - a measure of the time it takes for a packet to traverse a route (the router does not actually track how long packets are taking to reach the destination. The delay value, much like the bandwidth value, is a default value that can be changed by the network administrator). delay is measured in microseconds (usec). the value of the delay is based on the type of link to which the interface is connected. for FastEthernet link the value is 100 usec, Ethernet 100 usec, T1 (default serial) 20000 usec.

Reliability - is a measure of how rely is the link for the packet to be forwarded (how many packets are error or dropped). unlike delay, reliability is dynamically measured every 5 minutes. value of reliabilty is between 0 and 255. with 1 means minimally reliability and 255 means 100% reliable. if the value is 234/255 means that the link is 91.8% reliable.

Load - measure of how saturized is the link (amount of traffic saturizing the link). like reliability, load is calculated dynamically using 5 minutes-weighted average. of which value range from 0 - 255. in load, 1/255 is minimally loaded link (more desireable) and 255/255 means the link is completely saturated. there are two loads value tx (outgoing) and rx (ingoing).


the calculation of the metric

(K1 * bandwidth + K3 * delay) * 256

*Note: since K2, K4 and K5 are 0 then those factors are not calculated

bandwidth = (10,000,000/bandwidth)
delay = (sum of delay/10)


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DUAL
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DUAL - loop-free backup paths, routing loop avoidance, fast convergence
fast convergence through DUAL is achieved by the existence of loop-free backup paths

terminology
successor = a neighboring router that's used to forward the packet, this router has the least cost to reach the destination, in other words sucessor is the next hop for a route. is showed after the word via.

Feasible Distance = the lowest metric for a given route. this is showed after the administrative distance in "show ip route".

Feasible successor = a neighboring router that can reach the same destination as the successor and satisfies the feasibility condition.

Feasibility condition = a condition that the reported distance of the feasible successor to a given destination is less than the local distance (metric).

Reported Distance = metric that is advertised to other routers. this is simply a neighbor feasible distance for a destination.

a loop-free backup paths for a given destnation exists if there's another neighboring router (feasible successor) beside the current next-hop router (successor), of which metric (reported distance) for that destinatin is less than local current metric.

you may be wondering why if the feasible successor metric is less than the local current one, the router doesn't choose the path through the feasible successor? this is because the cost from current router to the feasible successor haven't been added to the reported distance of feasible successor. 'total cost' may be greater through feasible successor than
but this doesn't mean that if the successor failed, and all other neighbors RD (reported distance) is greater than this own FD (feasible distance), no route can be used to a given destination. if there is another path, and RD is greater than FD, that path will be used but it takes time for DUAL to recompute.
through successor.


auto-summary is on by default.
to make a manual summary, enter the following command at the interface level

ip summary-address eigrp  as-number network-address subnet-mask

as-number : eigrp process ID
network-address : summary network address
subnet-mask : mask for the summary

default route in EIGRP is usually set by the static route for the router that's connected to outside EIGRP network (ISP for example) and is redistributed with the router configuration command "redistribute static".

OSPF

OSPF (Open Shortest Path First) is one of the routing protocol most used. It's a link state routing protocol.

OSPF use bandwidth as its metric. The algorithm it uses to calculate the metric is to divide 100,000,000 by the bandwidth that the link has in bps, so a 100 Mbps link will have a metric value of 1.

OSPF forces you to design the network by dividing it into areas, there are two main type of area backbone area (usually called area 0) and nonbackbone area. OSPF also support different type of network in fact that there are different type of networks like point to point, broadcast (ehternet, Token Ring, FDDI), nonbroadcast (framerelay), etc..


there are also different kind of routers in OSPF. Designated Router is the router that do the brunt of the OSPF processing. DR and Backup DR is elected in every area (in every area - not so sure about this) through a complicated way (ospf priority, highest loopback ip, highest ip address assigned to this router)

usually a router running OSPF has a loopback interface to prevent the election of the DR through the highest physical ip address.

OSPF routers don't send routes instead they send link state advertisement (LSA). there are different kinds of LSA. Router LSA is sent by every OSPF router, Network LSA is sent by DR, and etc...

so, when you're configuring a network with OSPF (remember that OSPF is a classless routing protocol) you specify which area this network will be in.
example:
network 10.10.10.0 0.0.0.255 area 0


the complexity of OSPF is one of the reasons that many people choose EIGRP instead. but remember that EIGRP is only implemented by cisco routers.

routes redistributed into OSPF is divided into two 2 types. E1 routes increase the metric of the route as it is propagated through OSPF router (added cost at each hop). while E2 routes have its metric the same for all routers.

Routes from different AS is a E2 route.


routes summarization
Inter-Area
enter the following command in ABR router (Area Border). to announce the summary route to other OSPF areas
area xxx range A.B.C.D yyy.yyy.yyy.yyy

xxx : area of the summary route
A.B.C.D : ip address of the summary
yyy.yyy.yyy.yyy : subnet mask of the summary

for example an OSPF area 4 has the following subnet
172.16.100.16
172.16.100.32
172.16.100.48
172.16.100.60
in this example the summary address is 172.16.100.0 255.255.255.192 . then enter the following command to the ABR router of thearea
area 4 range 172.16.100.0 255.255.255.192


Inter-Domain
enter the following command to the ABR
summary-address A.B.C.D yyy.yyy.yyy.yyy

A.B.C.D : ip address of the summary
yyy.yyy.yyy.yyy : subnet mask of the summary


OSPF doesn't support IPX


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OSPF default values
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Hello time - 10 (multiaccess and point-to-point), 30 on NBMA
Dead time - 40 (dead time is the time for OSPF to wait before declaring the end router is down).

in order for two router establishing an adjacency, both router must have the same timers value and network type. those parameter is
-hello interval
-dead interval
-network type

five network types in OSPF:
- point-to-point
- broadcast multiaccess
- nonbroadcast multiaccess (NBMA)
- point-to-multipoint
- virtual links


OSPF multicast address:
224.0.0.5 = all ospf routers
224.0.0.6 = all DR routers

OSPF DOES NOT AUTOMATICALLY SUMMARIZE SUBNET AT MAJOR NETWORK BOUNDARY.


five types of OSPF LSPs(Link State Packets)
1.Hello - used to maintain adjacency with other OSPF routers.
2.DBD - Database Description, sent to other OSPF routers that contains an abbreviated list of the sending router's link-state database and used by the receiving routers to check against the local link-state database.
3.LSR - Link State Request, sent to request more information about any entry in the DBD.
4.LSU - Link State Update, used to reply LSR and to announce new information.
5.LSAck - Acknowledgement to LSU.


OSPF calculates the metric using the bandwidth of the link. the calculation is taken as per 100mbps, so if a link bandwidth is 100mbps then the cost is 1. you can change the reference-bandwidth the ospf command "auto-cost reference-bandwidth" (measured in mbps). it's good practice to change the reference-bandwidth on all router running ospf when you change it on a router.

ALTERNATIVELY, you can set a cost for an interface in OSPF without OSPF needing to calculate the cost anymore by entering the following command at interface level configuration:
ip ospf cost xxx

xxx : the number of the cost



DR - BDR

DR and BDR election is happen only in multiaccess network.

election of DR & BDR happen as soon as an interface of a router participate in OSPF routing. this can happen when a router boot up or a network command for an interface is enabled. because of this, a router with a lower ip address (or routerID) could be the DR if it happened to be the first router running OSPF that boots. once a router become a DR, it will be a DR until it fails, or interface shutdown.

election process:
1. DR: router with the highest OSPF interface priority.
2. BDR: router with the second highest OSPF interface priority
3. if OSPF interface priorities are equal, the highest router'ID is used to break the tie.

Determining router ID
1. use the IP address configured with the "router-id" command.
2. use the highest loopback interface address.
3. use the ACTIVE (interface must be in an up-up state, but not neccessarily included in OSPF activity) physical IP address.


YOU CAN CHANGE THE VALUE OF OSPF INTERFACE PRIORITY by entering the following command at interface level configuration
ip ospf priority (0-255)
because OSPF interface priority is set on interface level. it can be set that a router be the DR on a network and a DRother on another network.


every link on an OSPF has a state. this state tell us about it's status with the other end device.

"show ip ospf neighbor" can show you about neighbor OSPF routers, their status as DR/BDR/DRother and their state with the local router (2WAY / FULL). 2WAY is adjacency between DRother routers they don't send LSA to each other just hello packets, FULL is adjacency between DROther and DR.


router ospf process-id is a number between 1-65535. the process-id is only locally significant, means that it may differ between router running OSPF to establish an adjacency. this is different with EIGRP that the autonomous-number DOES NEED to match to form a neighboring.

When two routers have the same router ID in an OSPF, domain routing may not function properly. If the router ID is the same on two neighboring routers, the neighbor establishment may not occur.

Like RIP, OSPF requires the use of the "default-information originate" command to advertise the 0.0.0.0/0 static default route to the other routers in the area

RIP

RIPv1
RIPv1 is a classfull routing protocol. CLASSFULL ROUTING DOESN'T INCLUDE THE SUBNET MASK INFORMATION IN ITS ROUTING INFORMATION UPDATES. because RIP is a classful routing. when you enter a subnetted network, the IOS will automatically convert it to the corresponding classful network. for example, network 192.168.1.32 will be converted to 192.168.1.0. Because of this behaviour, there is a design issue in RIP. there shouldn't be two subnetted networks with the same classful network address reached by different interface (discontiguous subnet) from a router. RIP advertise classful network. the routing table entry in this router will be unstable (if the cost of both subnets are the same) or this router will send the packets load balanced through each route (because there are two entries for the same major network).

RIPv1 broadcast its routing entires through update packets. a single update packet, can hold up to 25 routing entries.

RIP implements split horizon, so routes learned from an interface is not sent when sending updates to that interface.

you can stop a router running a routing protocol (the command discussed next is supported by all routing protocol), in this case RIP, from sending routing advertisement such as periodic updates to an interface by entering the following command at router's global configuration level.

passive-interface interface-type interface-number

interface-type : type of the interface (FastEthernet, Serial, ..).
interface-number: number of the interface.

you might want to enter this in a case where there's no neighbor router running the same routing protocol on that interface.

Routers running RIPv1 are limited to using the same subnet mask for all subnets with the same classful network.

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RIP Timers
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RIP use periodic updates to update its routing table. therefore there are some timers associated with RIP. Here are the timers

Periodic Updates - 30 secs
Invalid Timer - 180 secs. if a route is not refreshed up to 180secs. the route is marked invalid by making it unreachable (rip do this by changing the metric to 16)
Flush Timer - 240 secs. 60 secs longer than invalid time. after flush timer expires, the route is removed from the routing table.
Holddown Timer - 180 secs. if a router learns about a route from another router that it's unreachable, the route still stay in the routing table up to the holddown timer before it's removed to give time for every router to learn about the unreachable route. any advertisement with the same or worse metric reporting the route will be ignored. however, if an advertisement telling a better metric, the entry will be renewed and the holddown timer will be cleared.

RIPv1 sends updates to 255.255.255.255, which means a local broadcast address. any router will block packets destined to this destination from going out.

however RIP might recognize a subnet network. examine the following routing table.

172.30.0.0/24 is subnetted, 3 subnets
R 172.30.1.0 [120/1] via 172.30.2.1, 00:00:03, Serial0/0/0
C 172.30.2.0 is directly connected, Serial0/0/0
C 172.30.3.0 is directly connected, FastEthernet0/0

You can see that the route to 172.30.1.0 is gotten from R (RIP). How can RIP know that this network's subnet mask is 24? this can happen if the network advertised and the interface that received the advertisement have the same major network (classful network). in this case, the interface receiving the 172.30.1.0 advertisement has an ip address with network id of 172.30.x.x

RIP may have more than one route for a destination, if there's more than one route with equal cost to the same destination. RIP will use one of these for load balancing. if you enter "show ip protocols" command. you can see this information in the RIP section.

Maximum path: 4

this means that there can be up to 4 redundant equal cost path to the same destination.


Boundary Router : any router with interfaces in more than one major classful network.
boundary router may want to summarize the subnets of one major network to another major network (in fact that RIP only advertise major networks)

if the route entry for an update sent out to a different major network interface. then the network addres in the route entry is summarized to the classful network and then advertised. so the in the receiving router, the entry in the routing table for those subnets is only one, that is the major network of the subnets.

when an RIP interface first come up, it will sent a request message to neighboor routers. neigboor routers running RIP will send response message to the requesting router. it evaluates each route entry. If a route entry is new, the receiving router installs the route in the routing table. If the route is already in the table, the existing entry is replaced if the new entry has a better hop count. The startup router then sends a triggered update out all RIP-enabled interfaces containing its own routing table so that RIP neighbors can be informed of any new routes.

RIP doesn't support VLSM either. in a case where there are subnets from the same major network is applied with different subnets. only the subnets with the same subnet mask as the interface address of the outgoing update are advertised.

Supernet route will not be advertised by classful routing protocol including RIP. imagine in a case that you're creating a static default route with the destination address is a supernet. and you want RIP to redistribute this default route through the "redistribute static" command. however, because it's a supernet route, that default route won't be advertised to neighboring routers.

if you want to propagate static default route through RIP, you can enter the following command at the router configuration level

default-information originate



RIPv2
classles routing protocol

A ROUTER RUNNING RIPv1 CAN STILL PROCESS AN RIPv2 MESSAGE, IT WILL JUST IGNORE RIPv2 SPECIFIC FIELD.

RIPv2 Message (packet) contains subnet information, next-hop (The Next Hop address is used to identify a better next-hop address).

Distance Vector Routing Protocol

Distance Vector Routing Protocol, as the name implies,
Distance : how far the destination from this router.
Vector     : the direction to forward the packet to the destination
DV RP doesn't know the full path to reach the destination, it only know how far the destination is, and the direction of the destination.

Terminology
Split Horizon - that a router should not advertise a network through the interface from which the update came.
Poison routing - a way for DV router to make a route removed from a table of neighboring router by making the metric of the route to be unreachable.

RIP
Routing Information Protocol (RIP) was originally specified in RFC 1058. It has the following key characteristics:
- Hop count is used as the metric for path selection.
- If the hop count for a network is greater than 15, RIP cannot supply a route to that network.
- Routing updates are broadcast or multicast every 30 seconds, by default.


EIGRP
Enhanced IGRP (EIGRP) is a Cisco proprietary distance vector routing protocol. EIGRP has these key characteristics:
- It can perform unequal cost load balancing.
- It uses Diffusing Update Algorithm (DUAL) to calculate the shortest path.
- There are no periodic updates as with RIP and IGRP. Routing updates are sent only when there is a change in the topology.