DHCP Snooping Agent 82 remote-id Problem

[ramsesak]

Hello,

I'm working with a switch C9200L-48P-4X, the version of IOS is IOS XE Software, Version 17.06.05. I'm trying to configure dhcp relay service but in I found a problem with remote-id string data. I configured "ip dhcp snooping information option format remote-id string TESTE" on switch. In my DHCP Server,  with a tcpdump analisis, the remote-d field of dhcp discover pack show "^A^ETESTE". I'm trying to remove this "^A^E" from my string data, but I don't know how to do that. I believe that characters should be some kind of suboption, maybe a flag or something similar.

I need to remove it to make my dhcp service starts working

[Peter Paluch]

Hello,

It would be very helpful if you could save the data captured by tcpdump on your DHCP server into a PCAP file (use "tcpdump -w filename.pcap ...") and share it here - it would help us see the contents of your DHCP Option 82 the way they are.

Regardless, however, I suspect that the string in the Remote ID suboption is preceded by two bytes - one is the a type identifier (since depending on the platform, there are different Remote ID formats available - MAC, hostname, user-defined string), and the other is the string length. If this is the case then it won't be possible to prevent the switch from adding those two bytes there. Instead, it will be necessary to configure your DHCP server to simply accept those two extra bytes.

Either way, let's focus on getting that PCAP file and sharing it here if it is okay by you. We'll be wiser afterwards.

Best regards,
Peter