Cisco

Cisco configuration examples

DNS

Router(config)# ip domain list 
Router(config)# ip domain name 
Router(config)# ip name-server

NetFLOWS

Router(config)# ip flow-export version 5 or 9
Router(config)# ip flow-export destination [IP Address] [Port]
Router(config)# ip flow-export source Vlan1 or Interface
Router(config)# ip flow-cache timeout active 1

Logging

Router(config)# logging on
Router(config)# logging host {IP_address | hostname}
Router(config)# logging trap severity_level
Router(config)# logging source-interface interface_type interface_#
Router(config)# logging origin-id {hostname | ip | string string}
Router(config)# logging facility facility_type
Router(config)# service timestamps log datetime show-timezone

Log tuning, disable syslog link status changes. This can be done on every interface where you don’t want receive these messages from with the following setting.

Router(config)#no logging event links-status

Time

Router(config)# clock timezone CEST 1
Router(config)# clock summer-time cest recuring
Router(config)# clock summer-time cest date 25 march 2007 \
                                       2:00 25 oct 2009 2:00
Router(config)# ntp server

Port Channel

Port Channels are a quick way to get more bandwidth by aggregating multiple connections in one virtual pipe. For instance, tie four gigabit ports together into a channel and it becomes a four gigabit connection.

Channels can also offer redundancy fault tolerance for physical connections. If one of the links involved in a channel loses connection, the channel will continue on with the existing ports and three quarters of the bandwidth. Ports involved in a channel must be on the same blade in a modular switch like a Catalyst 4500 or 6500. (These can be solve with later versions)

Configuring port channels has become much easier in recent IOS versions. First, designate the desired ports into a channel group.

Switch(config)# interface GigabitEthernet2/1
Switch(config-if)# description Core Connection
Switch(config-if)# channel-group 2 mode desirable
Switch(config)# interface GigabitEthernet2/2
Switch(config-if)# description Core Connection
Switch(config-if)# channel-group 2 mode desirable

The desirable option will create a channel to another Cisco switch in etherchannel format and drop a single channel if necessary. In contrast, using the on option would force a port channel, but would drop the entire channel if a single link.

Etherchannel is Cisco’s proprietary channel protocol, sometimes called PAGP or Port Aggregation Protocol. In order to create channel with a server or non-Cisco switch, the channel will have to be configured in LACP (Link Aggregation Control Protocol) format, which is a multivendor standard.

Switch(config)# interface GigabitEthernet2/1
Switch(config-if)# description Core Connection
Switch(config-if)# channel-group 2 mode passive
Switch(config)# interface GigabitEthernet2/2
Switch(config-if)# description Core Connection
Switch(config-if)# channel-group 2 mode passive

Using the active option instead of the passive mode option will force the ports into a LACP channel without negotiation much like the on option for PAGP. The entire channel will go down if a single line is disconnected and will not be fault tolerant.