Redundancy protocols (FHRP)

Status: draft

Notes on VRRPv2 and v3 / HSRPv1 and v2 / GLBP. Definitions are in crates/wpg-protocols/src/fhrp.rs, samples in templates/protocols/fhrp/.

How they are reached, and samples

id	Protocol	Layer below	Sample
`vrrpv3`	VRRPv3 (IPv4 addresses)	IPv4 protocol 112	`vrrpv3.wpg.yaml`
`vrrpv2`	VRRPv2	IPv4 protocol 112 (re-decoded when `version` is 2)	`vrrpv2.wpg.yaml`
`vrrpv3_ipv6`	VRRPv3 (IPv6 addresses)	IPv6 next header 112	`vrrpv3-ipv6.wpg.yaml`
`hsrp`	HSRPv1	UDP 1985	`hsrpv1.wpg.yaml`
`hsrpv2`	HSRPv2	UDP 1985 (re-decoded for a first octet of 1), UDP 2029 (IPv6)	`hsrpv2.wpg.yaml`
`glbp`	GLBP (basic)	UDP 3222	`glbp.wpg.yaml`

VRRP checksum (Internet checksum for v2; including the IP pseudo header for v3) and the address counts (count_ip_addrs / count_ipvx_addrs).

VRRPv2 and v3 share IP protocol 112 and differ only in the version nibble. Decoding starts as vrrpv3 and re-decodes as vrrpv2 when version is 2. When building, pick the definition you want.
VRRPv3 address family follows the IP version of the enclosing packet, but a field cannot be sized from a lower layer, so there are two definitions: vrrpv3 (IPv4) and vrrpv3_ipv6 (IPv6).
HSRPv1 and v2 share UDP 1985. The first octet is the version (0) in v1 and the first TLV type (1, Group State) in v2, so decoding starts as hsrp and re-decodes as hsrpv2 for 1. The 16-octet HSRPv2 virtual address is IPv4 (zero padded) or IPv6 depending on ip_version, so it is opaque bytes(16).
GLBP is undocumented; only the Hello TLV (IPv4 virtual address) is typed. Request/Response and Authentication TLVs keep their value octets.
Only clear-text authentication is typed: VRRPv2 auth_data (8 octets), HSRPv1 auth_data and the HSRPv2 Text Authentication TLV (both default to cisco). The HSRPv2 MD5 authentication TLV stays value octets, and no digest is computed.

Field reference of the protocols on this page (generated from the definitions):