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New Member

eigrp

How do I find out which route eigrp as taken to reach a particlur network, what am I looking for when I do sh ip eigrp topology ?

9 REPLIES

Re: eigrp

Hi Carl,

"sh ip eigrp topology" only displays feasible successors.

The routes which are present in routing table with an entry of "D" are the best route which will be used by EIGRP to reach a particular destination.

How ever if you waan a see all the entries in topology table you have to issue a command

show ip eigrp topology all-links

HTH, if yes please rate the post.

Ankur

New Member

Re: eigrp

Is a feasible successor a route that it could actually use ? and is says feasible distance FD

is 2816 , what does that mean ?

thanks

New Member

Re: eigrp

Yes,the feasability sucessor route is an alternative back up route in case the sucessor route goes down.

2816 is the cost.

The lowest cost to reach a destination is referred to as the feasible distance.

New Member

Re: eigrp

on this then where could i find the route that it has chosen, does sh ip eigrp top not tell me this ?

New Member

Re: eigrp

show ip route will show next hop or traceroute will give you hop-by-hop what you are looking for. Please rate if this helped.

Thanks!

New Member

Re: eigrp

so is there no command to show what routes its chosen, i thought this was possible ?

Re: eigrp

Hi Carl,

The routes which are chosen are the best routes and are only seen in routing table with "sh ip route" command.

There are no specific place they are stored because routing table is holding them.

In routing table for EIGRP you will see a symbol "D" which means that is the best route choosen by EIGRP and it may have a feasible successor in topology table. Incase the best route goes off the feasible successor available in topology able is then installed in the routing table.

So the best routes are available in routing table as that is the place where they should be ;)

HTH, if yes please rate the post.

Ankur

Re: eigrp

'show ip route eigrp' will display all eigrp routes installed in the IP routing table.

'show ip eigrp topology (net) (mask)' will display all eigrp routes learnt, that would include, successor and all feasible successors.

Take a look at the below example. 1.1.1.0/24 is installed in the routing table via the next hop address of 172.31.1.14. EIGRP topology table indicates the route being learnt from two sources, 172.31.1.14 & 172.31.1.12.

Route learnt from 172.31.1.14 is chosen as the successor because of the better metric (FD of 409600). Should this route go away, the route from the feasible successor (172.31.1.12) will become the successor.

R1#show ip route eigrp

1.0.0.0/24 is subnetted, 1 subnets

D 1.1.1.0 [90/409600] via 172.31.1.14, 00:00:53, Ethernet0/0

R1#show ip eigrp top 1.1.1.0 255.255.255.0

IP-EIGRP (AS 1): Topology entry for 1.1.1.0/24

State is Passive, Query origin flag is 1, 1 Successor(s), FD is 409600

Routing Descriptor Blocks:

172.31.1.14 (Ethernet0/0), from 172.31.1.14, Send flag is 0x0

Composite metric is (409600/128256), Route is Internal

Vector metric:

Minimum bandwidth is 10000 Kbit

Total delay is 6000 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 1

172.31.1.12 (Ethernet0/0), from 172.31.1.12, Send flag is 0x0

Composite metric is (2195456/2169856), Route is Internal

Vector metric:

Minimum bandwidth is 1544 Kbit

Total delay is 21000 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Let me know if it helped.

--Sundar

New Member

Re: eigrp

sh ip route xx.xx.xx.xx (ip address of destination) will show the next hop, if a route exists otherwise the default route is used.

traceroute xx.xx.xx.xx (ip address of destination) will show ip addresses of path (providing they are not masked).

sh ip eigrp topology xx.xx.xx.xx subnetmask

will show possible first hops and their costs.

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