Category Archives: Networking

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 »

Arista EOS 101

This is a simple short notes taken from Arista Configuration Essentials (ACE) Lab Guide CLI & BASH Enter bash switch# bash switch-bash$ ifconfig -a switch-bash$ top switch-bash$ cd /mnt/flash Upgrade EOS Upload EOS to switch switch# copy http://1.1.1.1/EOS/EOS-4.15.5M.swi flash: Verify image switch# dir flash: Configure boot image switch# boot system flash: EOS-4.15.5M.swi Verify boot-config switch#… 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 »

BGP Aggregate experiment

The BGP aggregate-address can be used to summarise a set of networks into a single prefix. For this post, I just wanted to show the difference between aggregate-address and aggregate-address with summary only. We have below topology. I’m going to summarise prefixes in R1. R1 config hostname R1 ! interface GigabitEthernet0/0 ip address 10.10.10.1 255.255.255.252… Read More »