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.
