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MAC address problem on VLAN procurve 2810

DavidHP_1
Occasional Visitor

MAC address problem on VLAN procurve 2810

I have two 2810 switches that are connected between 2 branch offices thru an IP VPN based on VLAN. A DHCP server is at branch office nr. 1. Clients in de branch office nr. 2 receive their IP address from the DHCP server. Everything is working, because it can connect to everything in branch office nr. 1.

But when I connect a client computer from branch office nr. 1 to the switch in branch office nr. 2 it receives an IP address from DHCP, but can't communicate with anything in both branch office networks.

After altering the MAC address of the NIC in the client computer, everything works fine.

Please help!
7 REPLIES
Tijl van der Steeg
Valued Contributor

Re: MAC address problem on VLAN procurve 2810

Have you cleared the arp cache?
"Clear arp"
DavidHP_1
Occasional Visitor

Re: MAC address problem on VLAN procurve 2810

No I didn't. Can this be automated?
Tijl van der Steeg
Valued Contributor

Re: MAC address problem on VLAN procurve 2810

You can do this with procurve manager plus and the command line wizard.

Maybe you can do a show arp first on one switch, see which entry is causing the problem, and maybe clear arp
Richard Brodie_1
Honored Contributor

Re: MAC address problem on VLAN procurve 2810

The default for mac-age-time is 300 seconds.

If you are physically moving the computers between sites, and not just swapping them on the bench, it sounds unlikely to be the problem, unless you move very fast.

Possibly the DHCP server is letting the system renew the branch 1 details, when it should be sending a NAK and issuing new ones. When you change the MAC, you get fresh details.

If so IPCONFIG/RELEASE might also work. Failing that I'd be firing up Wireshark on an affected PC, and looking at before and after DHCP packets.
Tijl van der Steeg
Valued Contributor

Re: MAC address problem on VLAN procurve 2810

I've had an issue like this, turned out to be corrupt ARP table. But you'll never know
Richard Brodie_1
Honored Contributor

Re: MAC address problem on VLAN procurve 2810

Rereading, I was thinking of the FDB rather than the ARP cache. Even so these things _should_ be timing out.

To be honest, I hadn't even considered that IP routing might be enabled on a low end switch like a 2810. Come to think of it, I'm not even sure you can.

Just throwing possbilities in, and hoping something will stick. There isn't really enough information to be certain.



Pieter 't Hart
Honored Contributor

Re: MAC address problem on VLAN procurve 2810

What subnets do you use at both branches?
the network at branch-2 need to know what traffic to consider "local" and what to forward through the VPN-tunnel!
Basically you'll need different subnets.

Probably the DHCP-request IS forwarded, but other traffic not!
NB! in the DHCP-request, the original (branch1) address is preferred to be renewed,
You'll need two dhcp-scopes each with the correct default gateway for each branch.