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Beginner

Cisco 2960X Routing Issue

Greetings,

 

I am troubleshooting what I think is strange routing behavior on a 2960 switch. Routing is currently disabled on the 2960 and I do have a default gateway set for management traffic, however, there is a routing entry with a different gateway specified for a specific host.  This is of course messing up communication between the switch mgmt IP and the host, which happens to be a network monitoring device.  I'm trying to figure out how this entry made it into the switch and if/how I can edit it.  I know if I enable routing and add a default route, traffic to this host is routed properly, but I would like to find another way.

 

OPSCENTER-2960-05(config)#do sh ip route
Default gateway is 10.55.2.193

Host Gateway Last Use Total Uses Interface

10.185.184.184 10.55.2.198 0:00 1729965 Vlan50

 

 The 10.55.2.198 address is a backup gateway with a much higher weighted route on the L3 device.  Perhaps my issue is one of design and the backup gateway should be plugged into the L3 device instead of the switch, but it's still strange the switch would substitute a different gateway then what was explicitly stated 10.55.2.193.  Any thoughts are appreciated.

 

Thanks!

 

Nick

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Accepted Solutions
Collaborator

Re: Cisco 2960X Routing Issue

Hi,

 

Could be icmp redirects. Do you have icmp redirects enabled on your routers. Try clearing the routes with "clear ip redirect" and "clear ip route *"

 

Thanks

John

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8 REPLIES 8
VIP Mentor

Re: Cisco 2960X Routing Issue

Hello,

 

Post the full config of your switch...

Beginner

Re: Cisco 2960X Routing Issue

Sure thing!  Here it is, though you'll see it's a very basic L2 config.

 

Nick

VIP Mentor

Re: Cisco 2960X Routing Issue

Hello,

 

how is 10.55.2.198, the backup gateway, connected to your switch ? And how is 10.55.2.193 connected ? If the hop count is the same, which ports on the 2960 are connected to the primary and the backup gateways ?

Highlighted
Beginner

Re: Cisco 2960X Routing Issue

The backup gateway 10.55.2.198 isn't directly connected to the switch, but rather a different switch stack.  This stack is connected to the primary gateway via port channel 2 (ports 1/0/47,1/0/48,2/0/47,2/0/48).  I guess I'm really confused as to how the switch knows about the backup gateway device in the first place.  With routing disabled and the gateway set to 10.55.2.193, I would expect all traffic to get forwarded to 10.55.2.193 (the L3 device) and it would sort out the routing.

 

For a better idea of the topology, both switch stacks plug directly into a L3 device by port channel.  The backup is plugged directly into the second switch stack; the config of which I haven't posted.  I read on another post something about 'extended host mode' though I haven't found anything more on that...

VIP Mentor

Re: Cisco 2960X Routing Issue

Hello,

 

your switch is in VTP mode transparent, is that by design ?

Beginner

Re: Cisco 2960X Routing Issue

VTP transparent mode is by design as we are not using it and in a multi tenant building.

Collaborator

Re: Cisco 2960X Routing Issue

Hi,

 

Could be icmp redirects. Do you have icmp redirects enabled on your routers. Try clearing the routes with "clear ip redirect" and "clear ip route *"

 

Thanks

John

**Please rate posts you find helpful**
Beginner

Re: Cisco 2960X Routing Issue

Thanks a lot, John.  Clearing the route didn't work, but clearing the redirect cache did.  +10 internets!

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