Information Technology Reference
In-Depth Information
RIPv2 Message Format
The RIPv2 message for mat takes advantage of the unused fields in the RIPv1 message
for mat by adding subnet masks and other information. Figure 10-8 shows the RIPv2 mes-
sage for mat.
0
1
2
3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
Command
Version
Unused (must be zero)
Address Family Identifier
Route Tag
IP address (1st route entry)
Subnet Mask
Next Hop
Metric
Address Family Identifier
Route Tag
IP address (2nd route entry - up to 25)
Subnet Mask
Next Hop
Metric
Figure 10-8
RIPv2 Message Format
The following describes each field:
Command:
Indicates whether the packet is a request or response message. The re-
quest message asks that a router send all or a part of its routing table. Response mes-
sages contain route entries. The router sends the response periodically or as a reply to
a request.
■
Version:
Specifies the RIP version used. It is set to 2 for RIPv2 and to 1 for RIPv1.
■
AFI:
Specifies the address family used. RIP is designed to carry routing information
for s everal different protocols. E ach ent r y has an AFI to indic ate the t y pe of addre s s
specified. The AFI for IP is 2. The AFI is set to 0xFFF for the first entry to indicate
that the remainder of the entry contains authentication information.
■
Route tag:
Provides a method for distinguishing between internal routes (learned by
RIP) and external routes (learned from other protocols). You can add this optional at-
tribute during the redistribution of routing protocols.
■
IP Address:
Specifies the IP address (network) of the destination.
■
Subnet Mask:
Contains the subnet mask for the destination. If this field is 0, no sub-
net mask has been specified for the entry.
■
Next Hop:
the destination.
■
