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Cisco Bug: CSCun26512 - dhcp relay support with URPF cause DROP at INGRESS using customer topo

Last Modified

Sep 17, 2018

Products (1)

  • Cisco Nexus 6000 Series Switches

Known Affected Releases

7.0(1)N1(0.103)

Description (partial)

Symptom:
dhcp relay support with URPF cause DROP at INGRESS using customer topo

Conditions:
configuring DHCP Relay and URPF on interface vlan 363 on the N6K-14a and N6K-14b switches, if the DHCP Discover (client broadcast) arrived at N6K-14b (Active HSRP), then the DHCP Relay will forward the DHCP discover packet from N6K-14b as uni-cast (using DHCP Relay) to N5K48-2 and then to the DHCP server, then the DHCP server could uni-cast a Offer back through N5K48-1 and over to N6k-14a, then these offers has to be forwarded to the N6K-14b since URPF is configured on the DHCP Discover was send from N6K-14b. 
The issue is, if this is the route that was traversed for the DHCP Offer, then once the DHCP Offers are send back to N6K-14b over the MCT, the MCT (VPC10) drops the DHCP Offers.
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