Juniper EX: How to Resolve Duplicate Packet/Ping Reply in Network Configuration

juniper-exloop

I'm having a issue with receiving duplicate packets in my network and I'm unsure what's causing it. A simplistic explanation of what's happening is this:

Server1 sends a ping request to Server2

Server2 receives the ping request from Server1, sends ping reply to Server1

Server1 receives two ping replies (DUP)

The network layout is pretty simple – here is a (poorly) drawn diagram:

http://i.imgur.com/jW0LoTU.png

Some things to note that I think is related:

  • The SW1.LAX.AGG switches each have RVI's from different subnets. We have a VLAN called "test" with subnets 10.0.0.0/24, 10.0.1.0/24 and 10.0.2.0/24. The VLAN interface has the first IP of each range assigned. The VLAN "test" has a "l3-interface" pointing to the proper VLAN interface.

  • When you ping an IP from another subnet (say pinging 10.0.1.200 while the primary IP on the machine is 10.0.0.200) it goes over the default gateway of 10.0.0.1 and gets the DUP ping reply. When pinging from a secondary IP on another subnet (10.0.2.200) using the ping -i eth1:0 there is no DUP reply.

  • When receiving the duplicate reply the TTL is not increasing or decreasing.

  • This is not a duplicate IP issue.

Any suggestion on how I can debug this further / is there something silly I'm missing?

Thanks!

Best Answer

Troubleshooting is required. First identify the culprit.

Turn off VRRP (or simply power off one of those routers). Does that fix it? If so look at the VRRP config. Otherwise, power off a VSS switch. Does that fix it? Start by identifying the problem...

Not sure if you are talking FEX's here but ideally those are NOT dual homed (as in your diagram), provided that your servers are. The proper way to do it is shown below.

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