routing issue at Layer switches

[interfacedy]

Hi Please see below diagram. A2, A1 and B2 are L3 switches and B1 is a PC device. A2 and B2 are connected with interface ip addresses 192.168.1.1 and 2 respectively. The static route is configured at B2, but not at A2. Question is why devices B1 and B2 at vlan 20 can ping device at device at vlan 10? we understand vlan 10 cannot ping vlan 20 because no static route. Thank you

[Giuseppe Larosa]

Hello @interfacedy ,

the absence of  a specific route on swich A2 for returning traffic to subnet 10.20.20.0/24 can be "fixed" by a default static route

if A2 has

ip route 0.0.0.0 0.0.0.0 192.168.1.2

this would explain what you see.

Hope to help

Giuseppe

[balaji.bandi]

You need to route back from B2 to A1 (same way you did A2 to B2 )

or run any IGP protocol to exchange routes easy

[paul driver]

Hello

---

@interfacedy wrote:

Question is why devices B1 and B2 at vlan 20 can ping device at device at vlan 10? we understand vlan 10 cannot ping vlan 20 because no static route.

---

I beleive B2 would be able reach either A1 and A2 to due to the fact that it having direclty connected interrface to A2 and a static route to A1 network.

However B1 WONT be able to ping either A1 or A2 from what you have stated and that is becasue as others have highliged A2 isnt aware of B1 network

[MHM Cisco World]

I think it complicate but 
Native VLAN is different in both SW, so arp broadcast is go from one SW to other through the mismatch Native VLAN, 
try make same native vlan in both SW and see the different.

[interfacedy]

@paul B2 shouldn't able to ping vlan10 because it has no return route. Why it is able to ping? Maybe something wrong

[MHM Cisco World]

 As I mention before it complicate, so
are you not config default GW in PC ?
are you config different native VLAN in both SW ?
try  change 
1- config default GW in PC 
or 
2- config same native VLAN in both SW 
and see result.

[paul driver]

@MHM Cisco World  native vlan has nothing to do with this - due to the fact the switch’s

show they are connected at layer 3

[paul driver]

Hello

i think you’ve misread  - I said B1 shouldn’t be able to ping and B2 should

[Jon Marshall]

Assuming there is no NAT on B2 which is unlikely if they are L3 switches then yes. I agree, something seems to be setup incorrectly if B1 can ping a device in vlan 10. 

Jon

[Giuseppe Larosa]

Hello @interfacedy ,

please can you post

show ip route

taken on switch A2.

The answer can be there.

if A2 and B2 are switches they should not support NAT .

Hope to help

Giuseppe