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Chapter 7
Multi-Layer Switching (MLS)
Removing MLS Cache Entries
If you do not want to wait for aging times to expire, or if you want to clear
the cache immediately, you can issue the clear mls entry command. This
command also has options that allow the network administrator to clear
specific cache entries instead of the entire table.
The syntax of the command is as follows:
clear mls entry destination ip-addr-spec source ip-addr-
spec flow protocol src_port dst_port [all]
The use of the all option keyword causes all MLS cache entries to be
removed. If you use specific IP addresses, ports, or protocols, specific cache
entries can be removed.
Acceptable MLS Topologies
T
here are few topologies that support MLS. Due to the nature of MLS,
only certain system topologies will allow candidate and enable packets to
transit the router and switch properly. If both candidate and enable packets
cannot be identified, no complete flow cache entry can be made. Acceptable
topologies include the following:
Router on a stick This includes one router (internal RSM/MSFC or
external) and one switch. See Figure 7.7.
Multiple switches, one router This is acceptable if only one switch con-
nects to the router and the switches are connected via an ISL trunk. See
Figure 7.8
Two routers, one switch This works, but it requires more work for the
MLS-SE. The packet must be rewritten twice to account for the hops
across two routers. It also requires the candidate and enable packets to be
identified for each router. See Figure 7.9
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