SNMPing the route entried of a cisco switch or router is right?

zhangstones · ‎03-24-2009

Dear everyone:

There are two routes to a same destination,but snmp can just identify only one

of them,exactly the bigger on,for instance:

GZ-THRJY-DSW-1.I>sh ip route 172.16.48.0

Routing entry for 172.16.48.0/24

Known via "ospf 100", distance 110, metric 21, type extern 1

Last update from 192.168.20.186 on Vlan5, 1w4d ago

Routing Descriptor Blocks:

192.168.20.54, from 192.168.0.4, 1w4d ago, via Vlan2

Route metric is 21, traffic share count is 1

* 192.168.20.186, from 192.168.0.4, 1w4d ago, via Vlan5

Route metric is 21, traffic share count is 1

192.168.20.57, from 192.168.0.11, 1w4d ago, via Vlan25

Route metric is 21, traffic share count is 1

======

But I use snmp to walk everything on this switch and redirect the result to a file. I searched the file afterwards and found that snmp only gave me one result:

RFC1213-MIB::ipRouteNextHop.172.16.48.0 = IpAddress: 192.168.20.54

,which is not in use(marked "*"),anyway.

Could you help me to solve the problem?

Can I trust the snmp to do sth like topology discovery?

MICHEL.HEGERAAT · ‎03-24-2009

The topology discovery won't rely on this.

In fact it relies only on the CDP tables.

So any connection between 2 cisco devices where CDP is active will be shown in the topology.

(except phones)

Cheers,

Michel

zhangstones · ‎03-24-2009

You might be right.

But consider a cisco and Huawei(and some Nokia fw ...) network environment.CDP is only used among cisco's,but snmp looks like a standard protocol and it can help finding some information which can be "show"(or "display")in a switch.I've tried that HuaWeis' can display all route by using snmp,but cisco can't.

That's what I'm looking for.

I actually want to get the routing information from devices , not only want to discover the topology,which I mentioned before is not excactly.