March 4, 2025 - Reading time: 9 minutes

Common Mistakes and How to Avoid Them 

When configuring BGP, several common mistakes can cause session failures, missing routes, or improper route propagation. These mistakes can cause sessions to remain in Idle/Active states or prevent advertised routes from being installed in the routing table.

Below are the most frequent errors, their causes, and how to troubleshoot them effectively. To view a detailed explanation for each issue, simply click the provided links.

Read more

February 15, 2025 - Reading time: 13 minutes

In the previous lesson, we established iBGP peering between two routers in the same Autonomous System (AS 2350) and configured network advertisements.

Last Lesson's Summary:

• iBGP Peering Setup – We configured two routers (Router0 & Router1) to form an iBGP relationship.
• Network Advertisements – Router0 advertised 50.50.50.0/24 and 70.70.0.0/16 into BGP.
• Reachability Requirements – iBGP neighbors must be IP reachable before a BGP session can establish.
• Synchronization & Auto-Summary – The configuration assumes that synchronization is disabled and auto-summary is off to ensure proper route advertisement.

We ended the lesson with a challenge to verify iBGP was properly advertising routes and to advertise Loopback1 on both devices.

Read more

February 5, 2025 - Reading time: 10 minutes

BGP (Border Gateway Protocol) is the backbone of the internet, enabling networks to communicate and exchange routing information. It allows routers to determine the best path for forwarding data between different networks, known as Autonomous Systems (ASes).

There are two types of BGP:

• eBGP (External BGP) – Used between different networks, like between two Internet providers or a company and its internet provider.
• iBGP (Internal BGP) – Used within the same network to keep routing consistent.

In this lesson, we'll configure iBGP between two routers within the same Autonomous System (AS) using a simple two-router setup.

Read more

January 21, 2025 - Reading time: ~1 minute

added privileged command:

November 15, 2024 - Reading time: 9 minutes

What's New:

updated spanning-tree calculations and logic

added switch global command:

    spanning-tree mode pvst

    spanning-tree mode rapid-pvst

    spanning-tree vlan [1-1005] forward-time [4-30]

    spanning-tree vlan [1-1005] hello-time [1-10]

    spanning-tree vlan [1-1005] max-age [6-40]

    no spanning-tree vlan [1-1005] forward-time

    no spanning-tree vlan [1-1005] hello-time

    no spanning-tree vlan [1-1005] max-age

added privileged commands:

    show spanning-tree summary

    show spanning-tree root

    show spanning-tree interface fastethernet PORT/PORT

    show spanning-tree interface gigabitethernet PORT/PORT

    show spanning-tree interface fastethernet PORT/PORT detail

    show spanning-tree interface gigabitethernet PORT/PORT detail

added switch interface configuration command:

    spanning-tree cost [1-200000000]

    no spanning-tree cost

    spanning-tree port-priority [0-240]

    no spanning-tree port-priority

    spanning-tree vlan [1-1005] cost [1-200000000]

    no spanning-tree vlan [1-1005] cost

    spanning-tree vlan [1-1005] port-priority [0-240]

    no spanning-tree vlan [1-1005] port-priority

other misc. fixes and improvements

August 29, 2024 - Reading time: 3 minutes

Added privilege command:
 show interfaces description

Added router privileged commands:
 show ip bgp
 show ip route bgp

 clear ip bgp *
 clear ip bgp * soft in
 clear ip bgp * soft out

 show ip ospf interface brief

 debug ip bgp
 no debug ip bgp

Added router BGP commands:
 neighbor A.B.C.D ebgp-multihop [1-255]
 no neighbor A.B.C.D ebgp-multihop [1-255]

 default-metric [0-4294967295]
 neighbor A.B.C.D weight [0-65535]
 neighbor A.B.C.D shutdown
 bgp default local-preference [0-4294967295]

 neighbor A.B.C.D route-map WORD in
 neighbor A.B.C.D route-map WORD out
 no neighbor A.B.C.D route-map WORD in
 no neighbor A.B.C.D route-map WORD out

 no neighbor A.B.C.D weight [0-65535]
 no default-metric [0-4294967295]
 no neighbor A.B.C.D shutdown
 no bgp default local-preference [0-4294967295]

 neighbor A.B.C.D next-hop-self
 no neighbor A.B.C.D next-hop-self

 neighbor A.B.C.D update source loopback <0-2147483647>
 no neighbor A.B.C.D update source loopback <0-2147483647>

 network a.b.c.d
 network a.b.c.d mask a.b.c.d
 no network a.b.c.d mask a.b.c.d
 no network a.b.c.d

 redistribute connected
 no redistribute connected
 redistribute connected route-map WORD
 no redistribute connected route-map WORD

 neighbor A.B.C.D password WORD
 no neighbor A.B.C.D password WORD

 auto-summary
 no auto-summary
 synchronization
 no synchronization

Added route-map command:
 set weight [0-65535]
 set local-preference [0-4294967295]
 set metric [0-4294967295]

Other optimization and improvements