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Answers to Review Questions

303

10.

A. Incoming packets must be destined to a MAC address that is asso-
ciated to the MLS-RP via the XTAG value. If the packet is not destined
for this address, the packet is not tagged as a candidate packet.

11.

A, B, D. Enable packets have more criteria to match than do candi-
date packets. Because the destination MAC address is different for
every hop, there is no way that a packet could match using the desti-
nation MAC address and still use MLS.

12.

A, D. MFSC and RSMs are layer 3 devices that are used in Catalyst
switches. Pattern matching and frame rewrites are done by the NFFC
and PFC.

13.

A, B, C. Although the rewrite engine can modify some fields in the IP
header, it does not change the IP addresses.

14.

B, C. The MLS-SE has to rewrite the CRC because it changes the val-
ues for the SMAC and DMAC. It calculates a new CRC for the new
frame.

15.

C. Once the MLS cache size is above 32K, chances are that the MLS-SE
will not be able to shortcut-switch all flows and packets will be sent to
the router.

16.

A, B. There are other commands as well that may inadvertently dis-
able MLS, but access lists no longer do. They can cause the cache to be
cleared, but now, since IOS 12.0(2), inbound as well as outbound
access lists are supported and do not disable MLS.

17.

B. Using header compression disables MLS on the configured inter-
face. Clear ip route is not a correct answer because it temporarily
clears the cache, but it doesn't disable MLS.

18.

D. The

mls rp ip

command is used on an external router, the first

command is invalid, and set mls enable is used to enable MLS on
a 5000 series switch.

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