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How to send/broadcast ipv6-mac maping cache update request for IPv6 IP

cn flag

We can update IPv4 neighbors by using arping command. I have used arping -A -I -c <interface_name> <IP_address_of_interface> with success.

what is the command to update mapping of IPv6 address and mac on router/gateway/nodes. we have observed when IPv6 address is removed from one node N1(RHEL-7.9 Node) and assigned to other node N2(RHEL-7.9 Node), mac address on router(Extreme Networks VDX 8770) dont get updated. It eventually gets updated but that time is not consistent. for this duration N2 is not reachable to gateway.

John Mahowald avatar
cn flag
Please edit your question to add the operating system of relevant hosts and routers. You tagged this Linux, but your comments indicate something else.
Score:0
cn flag

For service addresses, implement a high availability protocol that can move IP addresses quickly. For example VRRP via keepalived.

To manipulate the neighbor cache on one Linux host, use a command like ip neighbour flush to ${ADDRESS} The kernel will do discovery when it encounters that IP again, do something like ping ${ADDRESS} This does not affect other hosts' neighbor cache. Other platforms and IP stacks have different commands.

IPv6 neighbor advertisement is not using broadcast, it is using a targeted solicited multicast group. One way getting all hosts involved is playing with router advertisements and virtual MAC addresses. In other words, VRRP.

Edit: ND spec allows for unsolicited advertisements to all nodes multicast. But it is an optional MAY, so you might want to trigger it manually. See also on Server Fault: Linux tool for IPv6 unsolicited neighbor advertisements.

cn flag
This is not router or failover case or virtual ip, In this case when N1 who has IPv6-ip1 is shut off, and N2 is assigned with IPv6-ip1, mac table on router is still IPv6-ip1-mac-N1. it should be mac-n2. The router is not linux machine. question is from N2 - what can we do to update new mac on router. doing Ping is not working.
John Mahowald avatar
cn flag
See edit adding a mention about unsolicited advertisements. How fast do you need cutover to be? ND should figure it out in a leisurely few minutes, but seems like that's not fast enough for you.
cn flag
ndptool with -T is solution. thanks @John for pointer.
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