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In V1910 DHCP relay agent drops option 82 inserted by DHCP snooping

Skif
Occasional Visitor

In V1910 DHCP relay agent drops option 82 inserted by DHCP snooping

Hello,

 

I'm trying to use dhcp snooping with option 82 insertion on V1910-48G switch.

And it does it OK when dhcp clients and dhcp server are on the same VLAN.

Dhcp server gets request with option 82: agent.remote-id contains switch

MAC address and agent.circuit-id contains VLAN and port IDs.

 

When I move dhcp server to another VLAN and turn on dhcp relay, It receives

requests from the same clients without dhcp option 82.

 

What's wrong?

3 REPLIES
Fredrik Lönnman
Honored Contributor

Re: In V1910 DHCP relay agent drops option 82 inserted by DHCP snooping

I havent seen the V1910, but H3C lowend switches defaults to not relaying opt82. Try this:

dhcp relay information enable
dhcp relay information strategy keep

 

---
CCIE Service Provider
MASE Network Infrastructure [2011]
H3CSE
CCNP R&S

Skif
Occasional Visitor

Re: In V1910 DHCP relay agent drops option 82 inserted by DHCP snooping

Unfortunately in V1910 the only actions available from CLI are:

 

  initialize  Delete the startup configuration file and reboot system
  ipsetup     Specify the IP address of the VLAN interface 1 
  password    Specify password of local user
  ping        Ping function 
  quit        Exit from current command view
  reboot      Reboot system
  summary     Display summary information of the device.
  upgrade     Upgrade the system boot file or the Boot ROM program 

and DHCP Relay configuration page doesn't have appropriate options.

 

The only place where option 82 is mentioned is DHCP Snooping per-port configuration:

Interface State: Trust/Untrust
Option 82 Support: Enable/Disable
Option 82 Strategy: Drop/Keep/Replace

On client ports it's Untrust-Enable-Replace, on uplink port, where DHCP server sits - Trust-Disable-Replace, but it doesn't really matter.

 

By the way, HP V1910-48G is former 3Com BaselinePlus 2952, not H3C.

glink
Occasional Visitor

Re: In V1910 DHCP relay agent drops option 82 inserted by DHCP snooping

Hmm...  These were affordable switches for setup with my home lab in the basement.  I have cisco switches as well but they are primarly relegated to my test network and not production.  As it goes configuring DHCP Snooping and the No Option 82 command are quite trivial on my layer 3 cisco 3560's however Skif raises a valid concern as I would like to make sure I can disable the option 82 globally before enabling DHCP Snooping.  My DHCP Server is a raspberry pie on a different network and I want to ensure that there will not be issues before I enable this.  Any progress on this or is it what I can expect from a sudo layer 3 switch.