Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
New Member

Help with troubleshooting basic connectivity

This should be a rather simple scenario but couldnt get my head around it.

R1 and R2 are connected to SW1 (3560) in the same vlan and subnet but R1 cannot reach R2.

In order to try and isolate the problem I created an SVI for the vlan on SW1 and assigned it an ip add in the same subnet. From R1 i could ping the SVI address and vice-versa but from the SVI i could not ping R2. Making it seem the issue is isolated to between SW1 and R2

R1 is able to learn the mac address of R2

All concerned ports on the switch are in STP designated/forwarding state for the vlan

All concerned ports show as connected and assigned to the vlan (no err-disabled or notconnected)

I do not have access to R2 ( But as per requirement, if everyting is ok on the devices I have access to, I should be able to reach R2)

I looked through each line of the switch config and it is almost basic i.e. there is nothing strange present.

No ACL

No vlan-maps/filters

No private vlans

No SPAN sessions

No STP commands

etc etc

Reloaded both R1 and SW1

The one strange thing I noticed which I cant explain is when I do a debug ip icmp on R1 with pings to the SVI i see the icmp request/echo in the debug messages. But when i do a debug ip icmp on R1 and i ping to R2 i do not see icmp request/echo (samething when ping from SW1 to R2). I'm thinking atleast I should see my icmp request going out even if there were some ACL(or anything else blocking) on R2

At the end of the day, I am supposed to have a bgp session established between R1 and R2. But with this problem in place, it just remains active.

Any insights to what else might be checked on R1 and SW1 to establish this connectivity would be appreciated. (Unfortunately configs not available at this time)

5 REPLIES

Help with troubleshooting basic connectivity

Hi ,

I do not know why , but it seams like a lab task

Please post the config of the interfaces for R1, R2 and 3560.

Dan

New Member

Help with troubleshooting basic connectivity

It might be a Lab task

Like a I said R2 is not accessible but it is verified there is no issue with R2.

Interface configs are basic e.g. It was I that created the SVI on the switch and asssigned it an ip address.

Unfortunately configs are not available.

Re: Help with troubleshooting basic connectivity

Hi ,

In order to help you , you will need to post some outputs.

I do not belive that you would expect us to list all the things that we think that could couse this., without any input from you.

If the config contains some sensitive information then there is the sanitized config.

If the routers and the switch had a "basic"config then it would work or maybe we have some different views of "basic"

Regards

Dan

Help with troubleshooting basic connectivity

Please check if R1 and R2 are not having the same mac address.

This would explain the icmp behavior.

regards,

Leo

New Member

Help with troubleshooting basic connectivity

No they are not having the same mac address.

I cleard the arp cache on R1 but it was still able to learn the mac add of R2

I even put a static arp entry but all these did not make any difference.

242
Views
0
Helpful
5
Replies
CreatePlease to create content