Foundry NetIron M2404C and M2404F Metro Access Switches
Configuring Routing Information (Rev. 03)
Configuring IP Unicast Routing
© 2008 Foundry Networks, Inc.
Page 4 of 48
Static Routes
Static routes are manually entered into the routing table. Static routes are important in the
following cases:
•
When the router cannot build a route to a particular destination automatically.
•
When it is necessary to specify a gateway of last resort to which all unroutable packets will be
sent.
•
When, for security reasons, the user needs to make changes to the routing table of the router.
Static routes are never aged out of the routing table.
A static route must be associated with a valid IP subnet. An IP subnet is associated with a single
VLAN by its IP address and subnet mask. If the IP subnet is deleted or down, the static route
entries using this IP subnet will become inactive and will not be used, although they will be present
in the routing table.
The user can still see the configuration file by using the
show running-config
command in Privileged (Enable) mode.
The Static routes are configured by the
ip route
command in the Global Configuration mode. The
device remembers the static routes until they are manually removed. However, the
static routes
decisions can be overridden by the dynamic routing information through prudent assignment of
administrative distance values. Each dynamic routing protocol has a default administrative distance,
as indicated in
Table 2
.
NOTE
If the user wants to override a static route by information received from a dynamic
routing protocol, simply ensure that the administrative distance of the static route
is higher than that of the dynamic protocol.
The user can cause all static routes to be advertised by using the
redistribute static
command
in
the OSFP Router Configuration mode.
Special IP Interfaces
Some special IP interfaces defined in the application software are configured as part of the default
configuration and cannot be removed.
The special IP interfaces are as follows:
•
sw0
– this interface is attached to a VLAN named default. Its VLAN ID is 1. All the available
ports in the system are attached to this VLAN as untagged.
sw0
in an IP interface as any other
IP interface the user creates, but can only be attached to one VLAN (VLAN ID 1).
•
lo1-lo9
– these interfaces are not directly related to a VLAN. Note that they can never be in a
down state. The packets sent through these interfaces are looped back to the IP stack and are
then routed on a destination-IP-address basis.
•
OutBand
– the OutBand IP interface belongs to the Out-of-Band port. This port is destined
for debugging and management and cannot be used to pass data.
Loose Source and Record Route
The Loose Source and Record Route (LSRR) option provides the source of an internet datagram
with a means to supply routing information to gateways for forwarding the datagram to the
destination, and for recording the route information.