Last Updated on August 7, 2021 by Admin 3
You issue the following commands on RouterB:
Which of the following key strings will RouterB use when sending EIGRP packets? (Select the best answer.)
- Boson
- ExSim
- NetSim
- any of the three key strings
Explanation:
RouterB will use the key string Boson when sending Enhanced Interior Gateway Routing Protocol (EIGRP) packets. EIGRP supports Message Digest 5 (MD5) authentication of routing updates to prevent a router from receiving routing updates from unauthorized routers. Authentication is configured on a perinterface basis.
To configure an interface to authenticate EIGRP packets, you should first enter interface configuration mode by issuing the interfacetype number command from global configuration mode. Next, you should enable MD5 authentication by issuing the ip authentication mode eigrp autonomoussystemmd5 command in interface configuration mode. Finally, you should issue the ip authentication keychain eigrpautonomoussystem keychain command in interface configuration mode to specify the key chain that should be used. In this scenario, RouterB is configured for EIGRP autonomous system (AS) 19.
To create a key chain, you should issue the key chain chainname command from global configuration mode. The chain name is locally significant; it is used only to match a set of keys with a local router interface. Therefore, key chain names do not have to match between neighbor routers. In this scenario, RouterB is configured with the key chain name ExSim.
After you create a key chain, you must specify at least one key number by issuing the keynumber command in keychain configuration mode, where number is an integer from 0 through 2147483647. If multiple key commands are used to create multiple keys, the numbers do not need to be sequential. When sending EIGRP packets, the router will use the lowestnumbered key. Therefore, RouterB will use key 1 when sending EIGRP packets. When receiving EIGRP packets, the router will use any valid key that is configured on the router. Therefore, RouterB can use any of the keys when receiving EIGRP packets. However, the key numbers must match on each router; if a neighbor router uses the key string NetSim, it must also be assigned key number 37.
Each key can have only one authentication string. To specify the authentication string, you should issue the keystring text command in keychain key configuration mode, where text is a string of up to 80 casesensitive letters and numbers; the first character cannot be a number.
RouterB will use the key string Boson when sending Enhanced Interior Gateway Routing Protocol (EIGRP) packets. EIGRP supports Message Digest 5 (MD5) authentication of routing updates to prevent a router from receiving routing updates from unauthorized routers. Authentication is configured on a perinterface basis.
To configure an interface to authenticate EIGRP packets, you should first enter interface configuration mode by issuing the interfacetype number command from global configuration mode. Next, you should enable MD5 authentication by issuing the ip authentication mode eigrp autonomoussystemmd5 command in interface configuration mode. Finally, you should issue the ip authentication keychain eigrpautonomoussystem keychain command in interface configuration mode to specify the key chain that should be used. In this scenario, RouterB is configured for EIGRP autonomous system (AS) 19.
To create a key chain, you should issue the key chain chainname command from global configuration mode. The chain name is locally significant; it is used only to match a set of keys with a local router interface. Therefore, key chain names do not have to match between neighbor routers. In this scenario, RouterB is configured with the key chain name ExSim.
After you create a key chain, you must specify at least one key number by issuing the keynumber command in keychain configuration mode, where number is an integer from 0 through 2147483647. If multiple key commands are used to create multiple keys, the numbers do not need to be sequential. When sending EIGRP packets, the router will use the lowestnumbered key. Therefore, RouterB will use key 1 when sending EIGRP packets. When receiving EIGRP packets, the router will use any valid key that is configured on the router. Therefore, RouterB can use any of the keys when receiving EIGRP packets. However, the key numbers must match on each router; if a neighbor router uses the key string NetSim, it must also be assigned key number 37.
Each key can have only one authentication string. To specify the authentication string, you should issue the keystring text command in keychain key configuration mode, where text is a string of up to 80 casesensitive letters and numbers; the first character cannot be a number.
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