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Tag: cisco-switch

  • Unable to delete Stale/Obsolete statc routes in Cisco IOS

    Today, I had to troubleshoot a very peculiar problem on my Cisco Catalyst 3750 switches in two different sites. To cut a long story short, both the sites originally had IPSec VPNs over ADSL internet andtherefore static routes added to pass through their VPN firewalls. However, with a recent WAN migration with leased lines, all traffic moved to the WAN routers.

    However, the Static Routes became stale (obsolete) and we were unable to delete the static routes. The routes are not in the running config (no “ip route command in config”) and a reboot wouldn’t help.

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  • How to create VLAN Interfaces for InterVLAN Routing in Cisco IOS

    VLAN Interfaces are required in network scenarios where you have different VLANs and need Inter-VLAN switching on Layer3 (Routing capable) switches. Every VLAN that needs to be routed should have a VLAN interface.

    Let’s say we have VLAN 10 which hosts the subnet 192.168.10.0 subnet, VLAN hosts 192.168.20.0 subnet and VLAN 30 hosts 192.168.30.0 subnet. For Inter-VLAN routing to work, we need to have a VLAN interface setup for each of these VLANs and configured with an IP address from the same subnet which will be the default Gateway for that subnet. Lets say, 192.168.10.254,192.168.20.254.192.168.30.254 are the IP addresses for VLAN Interfaces of VLAn 10,20,30 respectively.

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  • How to Configure Multiple Interfaces in Cisco IOS

    In Cisco IOS, "interface range" command can help you configure multiple interfaces in one single command. This can be a range of switch ports on a module or multiple ports on multiple module be it FastEthernet or GigabitEthernet or vlans on a Cisco Switch or a Router.

    Sometimes, simple tasks like enabling a bunch of Administratively shutdown ports, assigning a range of switchports to a particular VLAN can become boring and tedious. This is where the "interface range"  can help where we can specify a comma seperated list of range of ports or vlans in the interface configuration mode and any command issued from there will apply to all switchports.

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