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 »

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 »

FIB vs RIB

Terminology: RIB – Routing Information Base FIB – Forwarding Information Base RIB This is a routing protocols database of routing prefixes that could potentially be installed in the routing table. Derived from the control plane, it is not used for forwarding. Every protocol such as OSPF, EIGRP, BGP has its own RIB and select their… Read More »

BGP RIB-Failure

When a Router receives a BGP UPDATE packet that contains Network Layer Reachability Information (NLRI) – this is, a route; the packet is processed in the next order: – Step 1. BGP checks for the NLRI (prefix received) against any BGP inbound filter configured on the Router. – Step 2. If the NLRI is not… Read More »