Technical data

System Administration
303561-A Rev 00
8-77
Unlike the show ip script command, which retrieves from the router’s active MIB
an aggregated view of data from IP routing tables and internal caches across all
slots, the Technician Interface
ip command retrieves the contents of the routing
table on a single slot that you specify. For this reason, the
ip command retrieves
information significantly faster than the
show ip command.
With the
ip command, you can examine:
• The entire contents of the routing table on any slot
• A subset of the total contents of the routing table on any slot
You limit the view of a routing table by applying filters -- subcommand options
and flags -- to the
ip command syntax. For example, you can enter ip routes -<s> ,
where -
<s> is a slot number you specify.
Interface Cache
The router operating system allocates a cache storage space to each
protocol-specific logical interface that you define on any physical circuit of the
router. The interface cache stores routing information relevant only to itself and its
own view of the networks external to the router.
This cache provides an initial source for an interface to retrieve at high speed the
best routes to any other IP destination address in your network. Upon receiving a
packet, the interface checks its local cache, then specifies processing for the
packet:
• Encaps processing -- The packet will be forwarded out of the interface.
• Reassembly processing -- The packet is for this router.
• Redirect processing -- An ICMP redirect packet is sent from the interface,
back to the source.
• Net Unreachable processing -- An ICMP net unreachable packet is sent from
the interface, back to the source.
• Host Unreachable processing -- An ICMP host unreachable packet is sent
from the interface, back to the source.
Note:
RIP and EGP routes are refreshed only on a slot that receives a route
update. Route ages may be different on each slot for this reason.