GARP and RA packet specifications for HA policy with fast IP move
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The following sections specify the GARP and RA packet specifications required by
Google Cloud when the haPolicy.fastIPMove backend service parameter is
set to GARP_RA.
GARP packet format for IPv4 traffic
The following fields are required when you use a GARP packet to trigger a
new leader.
Sender MAC address
MAC address of the sender VM instance (the new leader).
Sender IPv4 address
The /32 IPv4 address that is moving to the new leader.
Target MAC address
Broadcast MAC address: FF-FF-FF-FF-FF-FF
Target IPv4 address
Same as the sender IPv4 address.
ARP operation
ARPOP_REPLY: 2
RA packet format for IPv6 traffic
RA supports advertising multiple IPv6 prefix ranges in a single RA packet by
attaching multiple ICMPv6 prefix information
options.
When haPolicy.fastIPMove is set to GARP_RA, every IPv6 prefix range in a
single RA packet should be an exact match to a forwarding rule IP address, and
all of those forwarding rules must point to the same regional backend service.
If the set of IPv6 prefix ranges are served by different regional backend
services, the RA packet is treated as invalid and doesn't trigger a fast IP
move.
The following fields are required when you use an RA packet to trigger a
new leader.
Sender MAC address
MAC address of the sender VM instance (the new leader).
Sender IPv6 address
Link-local IPv6 address of the sender VM instance. This is not the IPv6
address that is moving to the new leader.
Target MAC address
All node multicast MAC address: 33-33-00-00-00-01
Target IPv6 address
IPv6 all node multicast address: FF02::1
IPv6 hop limit
255
ICMPv6 type
ND_ROUTER_ADVERT: 134
ICMPv6 options type
ND_OPT_PREFIX_INFORMATION: 3
Prefix information option prefix
The IPv6 prefix that is moving to the new leader. Bits after the prefix
must be zero.
Prefix information option prefix length
The length of IPv6 prefix that is moving to the new leader.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-29 UTC."],[],[],null,["# GARP and RA packet specifications for HA policy with fast IP move\n\nThe following sections specify the GARP and RA packet specifications required by\nGoogle Cloud when the `haPolicy.fastIPMove` backend service parameter is\nset to `GARP_RA`.\n\nGARP packet format for IPv4 traffic\n-----------------------------------\n\nThe following fields are required when you use a GARP packet to trigger a\nnew leader.\n\nRA packet format for IPv6 traffic\n---------------------------------\n\nRA supports advertising multiple IPv6 prefix ranges in a single RA packet by\nattaching multiple ICMPv6 [prefix information\noptions](https://www.rfc-editor.org/rfc/rfc4861#section-4.6.2).\n\nWhen `haPolicy.fastIPMove` is set to `GARP_RA`, every IPv6 prefix range in a\nsingle RA packet should be an exact match to a forwarding rule IP address, and\nall of those forwarding rules must point to the same regional backend service.\n\nIf the set of IPv6 prefix ranges are served by different regional backend\nservices, the RA packet is treated as invalid and doesn't trigger a fast IP\nmove.\n\nThe following fields are required when you use an RA packet to trigger a\nnew leader."]]
