After upgrading cluster from 4.10.47 to 4.11.25 issue is observed with Egress router pod, pods are in pending state. 

4.11.25

1. Upgrade from 4.10.47 to 4.11.25
2. Check if co network is in Managed state
3. Verify that egress pods are not created with errors like :
55s         Warning   FailedCreatePodSandBox   pod/******     (combined from similar events): Failed to create pod sandbox: rpc error: code = Unknown desc = failed to create pod network sandbox *******_d6918859-a4e9-4e5b-ba44-acc70499fa7c_0(9c464935ebaeeeab7be0b056c3f7ed1b7279e21445b9febea29eb280f7ee7429): error adding pod ****** to CNI network "multus-cni-network": plugin type="multus" name="multus-cni-network" failed (add): [ns/pod/d6918859-a4e9-4e5b-ba44-acc70499fa7c:openshift-sdn]: error adding container to network "openshift-sdn": CNI request failed with status 400: 'could not open netns "/var/run/netns/503fb77f-3b96-4f23-8356-43e7ae1e1b49": unknown FS magic on "/var/run/netns/503fb77f-3b96-4f23-8356-43e7ae1e1b49": 1021994
 

Egress router pods in pending state with error message as below:
$ omg get events 
...
49s        Warning  FailedCreatePodSandBox  pod/xxxx  (combined from similar events): Failed to create pod sandbox: rpc error: code = Unknown desc = failed to create pod network sandbox k8s_xxxx_379fa7ec-4702-446c-9162-55c2f76989f6_0(86f8c76e9724216143bef024996cb14a7614d3902dcf0d3b7ea858298766630c): error adding pod xxx to CNI network "multus-cni-network": plugin type="multus" name="multus-cni-network" failed (add): [xxxx/xxxx/379fa7ec-4702-446c-9162-55c2f76989f6:openshift-sdn]: error adding container to network "openshift-sdn": CNI request failed with status 400: 'could not open netns "/var/run/netns/0d39f378-29fd-4858-a947-51c5c06f1598": unknown FS magic on "/var/run/netns/0d39f378-29fd-4858-a947-51c5c06f1598": 1021994

Egress router pods in running state

Workaround from https://access.redhat.com/solutions/6986283 works :
Edit sdn DS in openshift-sdn namespace : 
- mountPath: /host/var/run/netns <<<<< /var/run/netns
  mountPropagation: HostToContainer
  name: host-run-netns   
  readOnly: true