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Distance vector routing protocols updates

Hey all,

I just need to confirm my info about distance vector routing protocols updates.

"Routers using a distance vector protocol must send all or a portion of their routing table in a routing-update message at regular intervals to each of their neighboring routers."

- RIP:

"RIP sends routing-update messages at regular intervals and when the network topology changes. When a router receives a routing update that includes changes to an entry, it updates its routing table to reflect the new route. The metric value for the path is increased by 1, and the sender is indicated as the next hop. RIP routers maintain only the best route (the route with the lowest metric value) to a destination. After updating its routing table, the router immediately begins transmitting routing updates to inform other network routers of the change. These updates are sent independently of the regularly scheduled updates that RIP routers send."

Does this behavior differ between RIPv1 and v2, and is there any difference between both regarding this issue, and what is the value of using "Triggered Extensions to RIP" if this is the default bevior of RIP, is it just the supression of the 30 seconds routing table flooding ?

- EIGRP: (advanced distance vector protocol)

On the other hand EIGRP uses an update packet at the start of a neighborship and also triggered updates at route entry changes (sending only the affected route), and then uses Query and reply (in the case of failure of a route and no available FS for it), with no periodic updates in EIGRP, am i OK here ?

Update packets are used to convey reachability of destinations. When a new neighbor is discovered, unicast update packets are sent so that the neighbor can build up its topology table. In other cases, such as a link-cost change, updates are multicast. Updates always are transmitted reliably.

Query and reply packets are sent when a destination has no feasible successors. Query packets are always multicast. Reply packets are sent in response to query packets to instruct the originator not to recompute the route because feasible successors exist. Reply packets are unicast to the originator of the query. Both query and reply packets are transmitted reliably.

What about IGRP ? (I assume that it sends periodic full routing table, plus triggered updates at route changes, but it doesn't use Query and reply packets, am i ok ?)

Thanks in advance,

Mohammed Mahmoud.


Re: Distance vector routing protocols updates


Does this behavior differ between RIPv1 and v2: NO

and is there any difference between both regarding this issue: NO

and what is the value of using "Triggered Extensions to RIP" if this is the default bevior of RIP, is it just the supression of the 30 seconds routing table flooding ?

This is only used in point-to-point interfaces and its used in low bandwidth links, updates are only sent if there's a change in the routing table.


You need to re-read it.

"EIGRP uses multiple packet types, all of which are identified by protocol number 88 in the IP header:

Hellos are used by the neighbor discovery and recovery process. Hello packets are multicast and use unreliable delivery.

Acknowledgments (ACKs) are Hello packets with no data in them. ACKs are always unicast and use unreliable delivery.

Updates convey route information. Unlike RIP and IGRP updates, these packets are transmitted only when necessary, contain only necessary information, and are sent only to routers that require the information. When updates are required by a specific router, they are unicast. When updates are required by multiple routers, such as upon a metric or topology change, they are multicast. Updates always use reliable delivery.

Queries and Replies are used by the DUAL finite state machine to manage its diffusing computations. Queries can be multicast or unicast, and replies are always unicast. Both queries and replies use reliable delivery.

Requests were a type of packet originally intended for use in route servers. This application was never implemented, and request packets are noted here only because they are mentioned in some older EIGRP documentation.

If any packet is reliably multicast and an ACK is not received from a neighbor, the packet will be retransmitted as a unicast to that unresponding neighbor. If an ACK is not received after 16 of these unicast retransmissions, the neighbor will be declared dead."

IGRP is too old to care ;)


Re: Distance vector routing protocols updates

Hi Vlad,

Nice respond here that reflects through understanding. The whole point here is that i am trying to consolidate a complete strong background about routing, so i am trying not to miss the small points, i know that IGRP is too old to care, but i need to have complete knowledge. After some readings, i found out that IGRP acts really simillar to RIP, with a complete routing update at the start, and then triggered routing updates at network changes, with periodic full updates, can you confirm that with me ?

Thanks very much,

Mohammed Mahmoud.

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