System information

BSR 64000 Configuration and Management Guide
9-32
RIP uses the hop count to rate the value of different routes. A directly connected
network has a hop count of one; an unreachable network has a hop count of 16. This
small range of metrics makes RIP unsuitable for large networks.
The route tag field in a RIP message allows boundary routers in an autonomous
system (AS) to exchange information about external routes. Route tags separate
internal RIP routes from external RIP routes that were imported from an Exterior
Gateway Protocol (EGP) or another IGP. Routers that support protocols other than
RIP should allow configuration of route tags for routes imported from different
sources.
The subnet mask field in a RIP (RIPv2 only) message contains the subnet mask
applied to the IP address to set the non-host portion of the address. If the subnet mask
field is not used, the subnet mask is calculated. On an interface where a RIPv1 router
operates on information in a RIPv2 routing entry, the following rules apply:
• Information internal to one network must never be advertised to another network.
• Information about a more specific subnet may not be advertised where RIPv1
routers would consider it a host route.
• Supernet routes (routes where a netmask is less specific than the natural network
mask) must not be advertised where they could be misinterpreted by RIP routers.
The next hop field in a RIP (RIPv2 only) message contains the next destination IP
address. A value of zero in this field indicates that the next destination is the origin of
the RIP message. To reduce unnecessary load on hosts that do not listen to RIPv2
messages. RIP update packets use IP multicast address 224.0.0.9.
Specifications
The BSR supports the following Request for Comment (RFC) specifications:
RFC 1058 — Routing Information Protocol
RFC 2453 — RIP Version 2