Category Archives: CISCO

Cisco IOS VTI

The use of Internet Protocol Security (IPsec) Virtual Tunnel Interfaces (VTIs) simplifies the configuration process when you must provide protection for site-to-site VPN tunnels. A major benefit of IPsec VTIs is that the configuration does not require a static mapping of IPsec sessions to a physical interface. IPsec VTI’s function like any other real interface… Read More »

Troubleshooting Boot Loader Prompt for Nexus 9K

If the system boots and falls into “loader>” prompt. Do the following steps. Step 1: Issue the command dir to check the directory and enter the command:boot nxos.9.2.1.bin ​ Step 2: Once the switch is boot up, set password for Nexus 9K, Step 3: Login to the switch. How to prevent Nexus 9K from dropping into “loader >” promptAs… Read More »

BGP as-path regular expressions

A regular expression is the character pattern that can be matched against an input string. Regular expressions can be built using letters (A through Z, a through z), numbers (0 through 9) and other keyboard characters, such as the exclamation point (!) or a tilde (~). A regular expression can be a single-character pattern or… Read More »

BGP Additional Paths

BGP routers only advertise the best path to their neighbors. When a better path is found, it replaces the current path. Advertising a path and replacing it with a new path is called an implicit withdraw. Since we only advertise the best path, a lot of other possible paths are unknown to some of the… Read More »

Default routes in BGP

There are 3 ways of advertising default route in BGP. Method 1: Using network 0.0.0.0 command. It requires only that the route 0.0.0.0 is present in the Interior Gateway Protocol (IGP) routing table. This is the preferred approach. Method 2: Using default-information originate command. It requires explicit redistribution of the route 0.0.0.0. This protects against… Read More »