3Com S7906E Configuration Manual page 602

IP Address: Destination IP address of the route. It can be a natural network, subnet or a host
address.
Metric: Cost of the route, 16 for request messages.
RIPv2 message format
The format of RIPv2 message is similar to RIPv1.
Figure 1-2 RIPv2 Message Format
0
Command
Header
Route
Entries
The differences from RIPv1 are stated as following.
Version: Version of RIP. For RIPv2 the value is 0x02.
Route Tag: Route Tag.
IP Address: Destination IP address. It can be a natural network address, subnet address or host
address.
Subnet Mask: Mask of the destination address.
Next Hop: If set to 0.0.0.0, it indicates that the originator of the route is the best next hop; otherwise
it indicates a next hop better than the originator of the route.
RIPv2 authentication message format
RIPv2 sets the AFI field of the first route entry to 0xFFFF to identify authentication information. See
Figure 1-3.
Figure 1-3 RIPv2 Authentication Message
Authentication Type: A value of 2 represents plain text authentication, while a value of 3 represents
MD5.
Authentication: Authentication data, including password information when plain text authentication
is adopted or including key ID, MD5 authentication data length and sequence number when MD5
authentication is adopted.
7 15
Version
AFI
IP address
Subnet mask
Next hop
Metric
1-4
Figure 1-2 shows it.
Unused
Route tag
31