Cisco Systems 78-11741-02 Wireless Office Headset User Manual


 
Configuring IP Routing Protocol-Independent Features
Specifying Default Routes
IPC-365
Cisco IOS IP Configuration Guide
Static routes that point to an interface will be advertised via RIP, IGRP, and other dynamic routing
protocols, regardless of whether redistribute static router configuration commands were specified for
those routing protocols. These static routes are advertised because static routes that point to an interface
are considered in the routing table to be connected and hence lose their static nature. However, if you
define a static route to an interface that is not one of the networks defined in a network command, no
dynamic routing protocols will advertise the route unless a redistribute static command is specified for
these protocols.
When an interface goes down, all static routes through that interface are removed from the IP routing
table. Also, when the software can no longer find a valid next hop for the address specified as the address
of the forwarding router in a static route, the static route is removed from the IP routing table.
Specifying Default Routes
A router might not be able to determine the routes to all other networks. To provide complete routing
capability, the common practice is to use some routers as smart routers and give the remaining routers
default routes to the smart router. (Smart routers have routing table information for the entire
internetwork.) These default routes can be passed along dynamically, or can be configured into the
individual routers.
Most dynamic interior routing protocols include a mechanism for causing a smart router to generate
dynamic default information that is then passed along to other routers.
Specifying a Default Network
If a router has a directly connected interface onto the specified default network, the dynamic routing
protocols running on that device will generate or source a default route. In the case of RIP, the router
will advertise the pseudonetwork 0.0.0.0. In the case of IGRP, the network itself is advertised and
flagged as an exterior route.
A router that is generating the default for a network also may need a default of its own. One way a router
can generate its own default is to specify a static route to the network 0.0.0.0 through the appropriate
device.
Enhanced IGRP (EIGRP) summary route 5
Exterior Border Gateway Protocol (BGP) 20
Internal EIGRP 90
IGRP 100
OSPF 110
IS-IS 115
RIP 120
EIGRP external route 170
Interior BGP 200
Unknown 255
Table 9 Dynamic Routing Protocol Default Administrative Distances (continued)
Route Source Default Distance