Multicast and Routing Guide K/KA/KB.15.15

5 Static Routing
This chapter describes how to add static and null routes to the IP route table.
Configuring an IPv4 Route
Static route Configure a static route to a specific network or host address
Null route Configure a "null" route to discard IP traffic to a specific network or host
address:
• Discard traffic for the destination, with ICMP notification to sender
• Discard traffic for the destination, without ICMP notification to sender
Syntax:
[no] ip route dest-ip-addr / mask-length [ next-hop-ip-addr
| vlan vlan-id | reject | blackhole ] [metric metric]
[distance1-255] [tag-value tagval] [name <name-str>]
Allows the addition and deletion of static routing table entries. A route entry is
identified by a destination (IP address/mask length) and next-hop pair. The next-hop
can be either a gateway IP address, a VLAN, or the keyword "reject" or "blackhole".
A gateway IP address does not have to be directly reachable on one of the local
subnets. If the gateway address is not directly reachable, the route is added to the
routing table as soon as a route to the gateway address is learned.
dest-ip-addr / mask-bits The route destination and network mask
length for the destination IP address.
Alternatively, you can enter the mask itself.
For example, you can enter either
10.0.0.0/24 or 10.0.0.0 255.255.255.0
for a route destination of 10.0.0.0
255.255.255.0.
next-hop-ip-addr This IP address is the gateway for reaching
the destination. The next-hop IP address is
not required to be directly reachable on a
local subnet. (If the next-hop IP address is
not directly reachable, the route will be
added to the routing table as soon as a route
to this address is learned.)
reject Specifies a null route where IP traffic for the
specified destination is discarded and an
ICMP error notification is returned to the
sender.
blackhole Specifies a null route where IP traffic for the
specified destination is discarded and no
ICMP error notification is returned to the
sender.
distance Specifies the administrative distance to
associate with a static route. If not specified,
this value is set to a default of 1. (Range: 1
to 255)
122 Static Routing