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Cisco Bug: CSCur13400 - DHCP Option 82 and Sub Option 5 issue in WLC 8.0

Last Modified

Feb 14, 2018

Products (1)

  • Cisco 5500 Series Wireless Controllers

Known Affected Releases

8.0(100.0) 8.0(110.0)

Description (partial)

Support is added for Cisco WLC to include Option 82, Sub-Option 5 when
relaying the DHCPDiscover message from the client. The Sub-Option 5 defines
the subnet, thereby allowing the GIADDR to only have one job, being just
the relay source, the address that the relay agent can be reached at. The
relay source can be any IP on the Cisco WLC that can easily be reachable
from the DHCP server, for example the management interface IP.

The pre-8.0 DHCP relay used the client facing dynamic interface to relay
the DHCP packet, which requires the DHCP-Server to be reachable from the
Client Subnet. My understanding is that this option allows me to set a
different interface (for example the management interface) as the source of
the DHCP packet.

Disregarding the DHCP Payload, only focusing on the IP-Packet the
controller generates itself the source is set to the correct interface
(management), but the source-MAC and the VLAN it is emitted on is set to
the client facing dynamic interface. In other words

Define WLC option 82 and sub option 5
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