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DHCP on 3750

iptrix
Level 1
Level 1

No idea if this is the place to ask, but I cannot figure this out. Got 3 3750's, and a bunch of ME3400 switches. One of the 3750 runs a dhcp server, but the problem is, I keep seeing that it's very, very hard for clients to actually get an IP. Sometimes they do, and then it's from the right dhcp scope, so everything appears correct .. only it can take like 10 tries to *get* the dhcpoffer message back to the client.

So I played with the debug function, and saw something interesting ..

Feb 16 21:47:51: DHCPD: DHCPDISCOVER received from client 01e0.91f5.ccc3.7e on interface Vlan00.

Feb 16 21:47:51: DHCPD: Sending DHCPOFFER to client 01e0.91f5.ccc3.7e (95.000.000.000).

Feb 16 21:47:51: DHCPD: Check for IPe on Vlan00 Feb 16 21:47:51: DHCPD: creating ARP entry (95.000.000.000, e091.f5cc.c37e).

Feb 16 21:47:51: DHCPD: unicasting BOOTREPLY to client e091.f5cc.c37e (95.000.000.000).

First 2 mentions of the mac address looks .. weird. Second 2 rows shows it differently. Is THIS why the dhcp server has such a hard time reaching back to the clients? I see from the debug log that it gets more or less all the requests. However using packet sniffers, I can see that the replies very seldom gets to the clients.

So what's going on? And why does the mac address look as above? I believe I'm running advancedipservices 12.2(44) on the 3750 that's the dhcp server atm, but I have no idea if this IS the problem :/ Been trying almost everything.

/Micke, Sweden.

17 Replies 17

I agree

ebarticel
Level 4
Level 4

Are all the clients on vlan 14, or each dhcp pool corresponds to a client vlan?

The reason I am asking is that the pools all have different default-router ip configured, but you have only 95.1.3.1 configured on vlan 14, and you mentioned that all clients are on vlan 14.

Do you have a ip helper address configured on the switches that supports it? If yes what is that ip?

Hope it helps

Eugen

Eugen has a good question. Why 4 dhcp pools if they are all on one Vlan?

Sent from Cisco Technical Support iPad App

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