There are some poor defaults that are used by Cisco. For some historical reasons there are some legacy default settings which you will want to remove on every device. The first one we'll talk about are log messages that are sent to the console board this is done by default and they tend to mix in with whatever you're typing for example you can be in the middle of typing an ip address as shown on the screen and then the log will pop up on the screen in between your commands a solution to this is simply sending all logs to memory buffer instead you can do so by typing the command no login console followed by the command logging buffer 8192 in this case 8192 is the size of the buffer followed by the debug command after this you can show all the logs by typing the command show log at the prompt to see the buffer contents the second four cisco default that we'll be talking about is that dns lookups are sent to broadcast address this can cause long delays as it tries to look for reverse lookups as you can see on the screen when you try to ping an src.org on the router you would see it would try to translate the address nsrc.org using the domain server 255.255.255.255. after some time it will return the error and recognize host or address you can fix this by simply disabling dns resolution completely to disable dns resolution you can use the command no ip domain dash look in configuration mode alternatively you can configure real dns servers using the command ip name server followed by the ip address of the dns server you would like to use with the examples on the screen the dns servers we're using are the google dns 184.108.40.206 and 220.127.116.11 please bear in mind that this can lead to delays when the network is down as you'll be unable to reach the dns servers the third poor cisco defaults that we'll be talking about is that typos are interpreted as hostnames to connect to very common one that happens is if you try to type write and you accidentally type w-r-t-i-e what happens is cisco would try to translate w-r-t-i-e to a host name using the domain server 255.255.255.255 and of course it will return bad ib address or hostname this also happens when you have a proper dns server configured as well a solution to this would be actually disabling this by typing the command transfer preferred not you would do this either under the line console this is for the console output or you would use the line btui04 interfaces which you would use for accessing the router using telnet or ssh the last and final more default we'll be talking about is that the router does not forward ipv6 traffic this solution to this is only on routers and not on layer 2 only devices remember layer 2 only devices are switches original routing capabilities to enable IPv6 traffic forwarding you would simply type the command "ipv6 unicast-routing" in the configuration mode.
© Produced by Philip Smith and the Network Startup Resource Center, through the University of Oregon.
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