4
The router forwards matching packets through the main route. When the main route fails, the route with
the highest preference among the backup routes is selected to forward packets. When the main route
recovers, the router uses it to forward packets.
Route recursion
To use a BGP route, static route (that is configured with a next hop but with no output interface), or RIP
route that has an indirectly-connected next hop, a router must perform route recursion to find the outgoing
interface to reach the next hop.
Link-state routing protocols, such as OSPF and IS-IS, do not need route recursion, because they obtain
directly-connected next hops through route calculation.
Route redistribution
Route redistribution enables routing protocols to learn route information from each other. A dynamic
routing protocol can redistribute routes from other protocols including direct routes and static routes. For
more information, see the respective chapters on those routing protocols in this configuration guide.
Displaying and maintaining a routing table
Task Command Remarks
Display information about the
routing table.
display ip routing-table
[
vpn-instance
vpn-instance-name
] [
verbose
] [
|
{
begin
|
exclude
|
include
}
regular-expression
]
Available in any view
Display information about routes
permitted by an IPv4 basic ACL.
display ip routing-table
[
vpn-instance
vpn-instance-name
]
acl
acl-number
[
verbose
]
[
|
{
begin
|
exclude
|
include
}
regular-expression
]
Available in any view
Display information about routes to
the specified destination.
display ip routing-table
[
vpn-instance
vpn-instance-name
]
ip-address
[
mask
|
mask-length
] [
longer-match
] [
verbose
]
[
|
{
begin
|
exclude
|
include
}
regular-expression
]
Available in any view
Display information about routes
with destination addresses in the
specified range.
display ip routing-table
[
vpn-instance
vpn-instance-name
]
ip-address1
{
mask
|
mask-length
}
ip-address2
{
mask
|
mask-length
} [
verbose
]
[
|
{
begin
|
exclude
|
include
}
regular-expression
]
Available in any view
Display routing information
permitted by an IPv4 prefix list.
display ip routing-table
[
vpn-instance
vpn-instance-name
]
ip-prefix
ip-prefix-name
[
verbose
] [
|
{
begin
|
exclude
|
include
}
regular-expression
]
Available in any view
