Adj-5-resolve-req-fail Adj Resolve Request Failed | For Work

Here’s a concise draft for documenting or reporting the error:

Engineers generally recommend three paths to resolution, ranging from configuration workarounds to permanent software fixes. 1. Disable CEF Neighbor Optimization (Primary Workaround)

CEF maintains a Forwarding Information Base (FIB) and adjacency table separately. If the FIB points to an adjacency entry that has been removed (e.g., due to a flapping interface or VRF change), the resolve request will fail. This is often seen after line card resets in distributed platforms (Catalyst 6500/6800, ASR9k). adj-5-resolve-req-fail adj resolve request failed for

: Several IOS versions (specifically 15.0(2)SE and early 15.2 releases) have documented bugs (e.g., CSCuo89272 CSCts29063

For VLAN subinterfaces or bridging scenarios, if the Layer 2 encapsulation doesn't match the neighbor's expectations – e.g., native VLAN mismatch on a trunk, or missing encapsulation dot1Q – the router cannot build the rewrite header. Here’s a concise draft for documenting or reporting

In some security-hardened routers, ARP or ND packets destined for the CPU are rate-limited by CoPP. If ARP requests for the next-hop IP are being dropped by the control plane, the adjacency never resolves, triggering the error.

Some reports suggest the error is more prevalent when traffic traverses an EtherChannel. If the FIB points to an adjacency entry

When the switch or router needs to forward a packet but cannot find a valid MAC address in its ARP table for the destination IP, it attempts an "Adjacency Resolve". If this request fails—often due to a software timeout or a logic error where the device incorrectly reports a failure despite having valid ARP data—the %ADJ-5-RESOLVE_REQ_FAIL alert is triggered. Common Causes

While this log can occur during normal network timeouts, it is most frequently associated with Cisco bugs like or CSCug43307 . In these cases: