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Why can't my router ping another router across a layer 3 switch?

Posted on 2014-10-02
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Last Modified: 2014-10-14
I have a strange issue I can not understand - basically I have the following setup:

Router1(172.16.10.254) ---- Layer 2 Switch ---- Layer 2 Switch ---- Router2(172.16.10.1)
PC1(172.16.10.222)---- Layer 2 Switch ---- Layer 2 Switch ---- Router2(172.16.10.1)

I can successfully ping from PC1 to Router2, but unable to ping from Router1 to Router2. I am no expert on networks/switches, but thought it might have something to do with port settings.

Any thoughts?

Router1 is a basic router (Linksys X1000).
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Question by:Flipp
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Expert Comment

by:wakatashi
ID: 40356524
Suggest checking that the subnet mask is set correctly on the PC and the two routers.
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Author Comment

by:Flipp
ID: 40356532
255.255.255.0 is set on PC, two routers.

It is only traffic between Router1 and Router2 which leaves Switch1 to Switch2 that has an issue.

Was thinking that we should try and inspect traffic for some type of vlan tagging but never performed this and dont really know what I am looking for.
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Author Comment

by:Flipp
ID: 40356534
Traffic between PCs and both routers are fine ..... this is giving me a headache :)
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Expert Comment

by:wakatashi
ID: 40356537
How are you doing the ping from Router1?  Are you telnetting/ssh-ing into a command-line interface?
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Expert Comment

by:R_Edwards
ID: 40356843
I am trying to figure out exactally how you have the connections from router 1 --> switch--> switch --> router 2, from PC 1 can you ping both routers?  have you looked @ the firewalls on the router?  are there ACL's on the switches, or any routes?

thanks
-=Richard
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Expert Comment

by:wakatashi
ID: 40356852
...and are the switches layer 2 or layer 3?

 (the diagram says layer 2, but the subject line of the question says layer 3)
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Author Comment

by:Flipp
ID: 40356960
Sorry for the confusion on layer 2 v layer 3. In fact one switch is managed by a 3rd party and they only informed me late today it is only a Layer 2.

Let me try and explain the network a bit better with attached.

We have a fairly basic setup with two switches connected, but a 2nd internal router. Strange thing is that other devices like the PC can ping both routers, but the routers can not ping each other.
NetworkDiagram
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Assisted Solution

by:wakatashi
wakatashi earned 500 total points
ID: 40357034
As a temporary test, try unplugging the PC from the Netgear switch, and connect the Cisco router directly into the same port of the Netgear switch that you just unplugged the PC from.  

See if you can ping now.  If you can, it suggests a faulty switch port, or something weird going on with the Juniper switch.  If you can't, we've at least ruled that out.
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Author Comment

by:Flipp
ID: 40358202
Yes we plugged the cisco directly into netgear and everything worked without Juniper. But I need the Juniper as it is our PoE for phone system.
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Accepted Solution

by:
Flipp earned 0 total points
ID: 40358643
News just in ..... port misconfiguration ..... 3rd party had changed port mode to trunking and needed to be access.

:-z
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Expert Comment

by:wakatashi
ID: 40358814
Great, so with the reconfiguration of the Juniper switch, is the problem solved?
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Author Comment

by:Flipp
ID: 40358855
Yes
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Expert Comment

by:wakatashi
ID: 40358930
Great!
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Author Closing Comment

by:Flipp
ID: 40379414
Thank you for your input ... I really appreciate the support EE provides through the community of experts. In this situation the solution we worked out through troubleshooting outside of EE.
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