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Chapter 13 RIP Configuration
Confidential and Proprietary Information of ZTE CORPORATION 171
RIP Timers
RIP uses numerous timers to regulate its performance. These
include a routing-update timer, a route-timeout timer, and a
route-flush timer. The routing-update timer clocks the interval
between periodic routing updates.
This is done to help prevent congestion, which could result from
all routers simultaneously attempting to update their neighbors.
Each routing table entry has a route-timeout timer associated
with it. When the route-timeout timer expires, the route is
marked invalid but is retained in table until the route-flush timer
expires.
RIP Packet Format
Figure 83 illustrates the IP RIP packet format.
F
I G U R E
8 3 I
P
R
I P
P
A C K E T
Following descriptions summarize the IP RIP packet format fields
illustrated in Figure 83.
ƒ
Command — indicates whether the packet is a request or a
response. The request asks that a router send all or part of its
routing table. The response can be an unsolicited regular
routing update or a reply to a request. Responses contain
routing table entries. Multiple RIP packets are used to convey
information from large routing tables.
ƒ
Version number — specifies the RIP version used. This field
can signal different potentially incompatible versions.
ƒ
Zero— this field is not actually used by RFC 1058 RIP; it was
added solely to provide backward compatibility with pre
standard varieties of RIP. Its name comes from its defaulted
value: zero.
ƒ
Address-family identifier (AFI)— Specifies the address
family used. RIP is designed to carry routing information for
several different protocols. Each entry has an address-family
identifier to indicate the type of address being specified. The
AFI for IP is 2.
ƒ
Address— Specifies the IP address for the entry.
ƒ
Metric— Indicates how many internetwork hops (routers)
have been traversed in the trip to the destination. This value
Routing
Updates