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BubaKukin
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Joined: Thu Feb 08, 2018 4:36 pm
Location: Moscow, Russia

DHCP snooping and optiion82

Sat Oct 12, 2019 6:20 pm

I'm testing CRS326-24G+2S, ROS 6.45.6.

One bridge, 5 vlans (with 5 VIFs), vlan filtering ON, dhcp-snooping ON, option 82 ON.
Vlan 11 for testin purposes.

DHCP server connected to port 2 (pvid 11, untag vlan 11, trusted)
Client connected to port 15 (pvid 11, untag vlan 11, untrasted)

When client connects and send DHCPDISCOVERY, the server receives 2 packets: first WITHOUT option 82 then second (same packet) WITH option 82.
Why? This is not valid for my DHCP-server, the configuration of which depends on option 82.

But if I turn off hw-offload on port 2, then the server receives only one packet. And packet contains option 82.

In this case, how do I understand the following (on wiki page):
Note: Currently only CRS3xx devices fully support hardware DHCP Snooping and Option 82. For CRS1xx and CRS2xx series switches it is possible to use DHCP Snooping along with VLAN switching, but then you must make sure that DHCP packets are sent out with the correct VLAN tag using egress ACL rules. Other devices are capable of using DHCP Snooping and Option 82 features along with hardware offloading, but you must make sure that there is no VLAN related configuration applied on the device, otherwise DHCP Snooping and Option 82 might not work properly. See Bridge Hardware Offloading section with supported features.
Which is true:
1. CRS326-24G support DHCP Snooping and Option 82 with hardware offloading and VLANS.
2. Or CRS326-24G NOT support DHCP Snooping and Option 82 with hardware offloading and VLANS.
3. It may be a bug and will be fixed later.

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