Routing one way, but not the other?

[Kgrevemberg]

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Update to problem on Page 2

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Hey guys, hoping I can get some help with a little issue I'm having.

So recently we deployed a switch to "Zone B" to extend a slice of our network to that zone for certain services.

From Router B, we can ping and traceroute to the switch no problem.

From Router A, pings and trace stops at Router B.

Router A shows that it know to go to Rtr B to get to the switch.

If I place a static route in RTR A I get the same results.

I also have no control over Zone B Cloud, they are tracking the issue and also looking into possible problems.

Any ideas about this?

On a basic level, I  can't seem to figure out why a traceroute would stop at a router that can successfully traceroute to the switch.

Any ideas are greatly appreciated

[balaji.bandi]

Post your both router config.

If router B reachable to Switch, router A also should do as long as you routing on place.

What IP Sub-net are in router A ?

BB

[Kgrevemberg]

I cant post configurations due to the classifications of these devices. But I can answer questions to the best of my abilities.

Router A and Router B each have several different networks on them via sub interfaces ie. g1/0.x

They communicate to each other specifically over G0/0 as an ip interface with x.x.241.0/252 subnet.

[Troy Jackson]

Can you source the ping from Router B's G0/0 interface to the switch?

[Kgrevemberg]

Even with that source it stops at the incoming interface for RTR B.

thanks for your reply

[Troy Jackson]

So pinging from Router B fails when sourced from the G0/0 interface? Have you tested ping and traceroute from the switch to Router A? Could zone B have a transparent firewall and are they still looking for an issue?

[Kgrevemberg]

Thanks for your reply.

We are unfortunately unable to log into the switch to do this issue currently. 

the only configurations it really has on it is an interface vlan with ip address.

Zone B department is still looking for issues on their side but not convinced its their problem.

[Meheretab Mengistu]

Hi,

When you PING from a router, it uses the outgoing interface as a source interface unless you provide source interface. For example, when you ping the Switch from Router B, it sources the ping request from interface Gi0/2. 

When you ping from Router A or Router B's source interface Gi0/0, you are not getting any result. It indicates that there is no route from the subnet where Gi0/0 is part of, or there is some kind of ACL which blocks that subnet. Could you check for those two things?

HTH,

Meheretab

[Kgrevemberg]

Thanks for your reply.

However in my original statement I did state that Router B can trace/ping to the switch with and without sourceing the ping/trace.

Router A knows about the network existing via router B when you show ip route, but for some reason the pings/traces wont make it past router B even when you source the ping/traces.

Also we have no ACLs regarding that network

Again, thanks for your help

[pchiava]

Sounds to me like the switch doesn't have it's default-gateway set to point back to RTR-B, since the switch is only part of RTR-B's network and RTR-A is one hop away it needs a gateway to point too as it's next hop so it knows how to get to the unknown network that RTR-A is part of.

Alternately you can add an interface in RTR-A that is part of the switch's network, then routing is irrelevant since they will both be part of the same broadcast domain.

Hope this helps out.

[Kgrevemberg]

*since the switch is only part of RTR-B's network and RTR-A is one hop away it needs a gateway to point too as it's next hop*  I like this answer, thats probably what it is

"Alternately you can add an interface in RTR-A that is part of the switch's network"  Can this be done if is a /252 network and Router B and the switch are using the two available ip's?

[Meheretab Mengistu · Accepted solution]

Thanks for the update.

Let's assume that the switch does not have a default gateway configured. As a work around, attempt running NAT on Router B as follows to determine whether it is a default-gateway issue:

int gi0/0
ip nat inside
int gi0/2
ip nat outside
ip nat inside source list 100 interface gi0/2 overload
!
access-list 100 permit ip x.x.241.0 0.0.0.3 any
!

HTH,
Meheretab

[Kgrevemberg]

int gi0/0
ip nat inside
int gi0/2
ip nat outside
ip nat inside source list 100 interface gi0/2 overload
!
access-list 100 permit ip x.x.241.0 0.0.0.3 any
!

Going to try this.

[Kgrevemberg]

int gi0/2
ip nat outside
ip nat inside source list 100 interface gi0/2 overload

should that command go on g0/2? I cant input the red part.

G0/2 should be the correct port as its the outgoing interface but the command isnt jiving 

[Kgrevemberg]

ah, sorry i figured it out.

global config