weird DHCP issue

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Jun 28th, 2008
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I am facing a weird DHCP problem. Here is the setup :

Cisco 3560 switch with three VLANs is connected via 802.1q trunk port to the LAN port of Riverbed wide area application device. LAN port on riverbed is also a trunk port. The WAN port of Riverbed device is connected to a Cisco 2800 router ethernet trunk port configured for these three vlans.

The 2800 router is configured as DHCP server for the three vlans. The problem is that ONLY DHCP is not working in this setup. If I assign a static IP address on workstations connected to 3560 switches I am ok with the connectivity.

The sniffer trace on Riverbed device indicates that the DHCP packet arriving from 3650 switch have different VLAN ID from what is configured on 3650 as well as the DHCP request packets are "FRAGMENTED".

Cisco 3650 switch has VLAN ID 10,110 and 210. The DHCP discover packet when it leaves trunk port and arrives on Riverbed is showing VLAN ID 3 and DHCP request packet has VLAN ID 75. When it leaves Riverbed WAN port definitely Router will discard it cause of unknown VLAN ID.

Any suggestions/ideas would be appreciated!!

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Edison Ortiz Sat, 06/28/2008 - 08:22
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Try connecting the router directly to the switch, if it works, then the problem is with the Riverbed device and its configuration.



daniel.lukic Sat, 06/28/2008 - 17:08
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Hi Fawad,

it may be an issue of the Steelhead Appliance. I would contact Riverbed's support with such an issue.

To analyze the problem, you could force the Steelhead to bypass mode (you may simply turn the Steelhead off for a test). If DHCP works with the Steelhead in bypass mode, i would assume it's a problem caused by that WAN-Optimizer.

Regards, Daniel


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