Manual Summarization with BGP on Cisco Routers

March 22, 2018 at 8:57 pm

BGP

One of the topics that will be featured in my upcoming CBT Nuggets module, Border Gateway Protocol (BGP) – Advertising NLRI, manual route summarization in BGP. This post serves (as well as more to follow) cover the highlights of the video coverage.

There are two methods of performing aggregation with BGP on a Cisco router. You can create a static route that represents the aggregate and then advertise that route using the network command. Or, you can use the aggregate-address command.

Here is an example of the static route approach:

router bgp 65100
   network 192.168.192.0 mask 255.255.248.0
   neighbor 192.168.1.220 remote-as 65200
!
ip classless
ip route 192.168.192.0 255.255.248.0 Null0

Notice how the static route directs to the bit bucket (Null0). This is because it is not an actual network destination. It is an artificial construct to permit the route in the routing table so we can use the network command in BGP. There will be more specific entries in the routing table covered by this advertised summary and the router can follow those instructions. Should all the more specific entries be removed, then the static route has traffic discarded for the summary (this is the desired behavior, typically).

With the aggregate-address command approach, you ensure component routes of the summary exist in the BGP table (thanks to the network statement or redistribution), and the summary address is advertised via BGP. Here is an example:

router bgp 65100
 aggregate-address 192.168.192.0 255.255.248.0 summary-only
 redistribute eigrp 100
 neighbor 192.168.1.220 remote-as 65200

Note that if you forget the summary-only keyword with the aggregate-address command, you will advertise the summary as well as the specific routes. A future post will demonstrate when this approach might be useful.

Cisco – Migrating from STP to RSTP

February 11, 2018 at 8:05 pm

CCIE

A frequent CCIE-level written exam topic is STP (PVST+) to RSTP (Rapid-PVST) migrations. This post covers the high points you should be aware of.

Some Quick Notes

  • BackboneFast and UplinkFast are no longer necessary in RSTP environments as the equivalent advantages are built-in to RSTP
  • BPDUs are version 2 in RSTP which is compatible with version 0
  • All ports now send BPDUs and they act as a keepalive mechanism
  • The new port roles are designated, root, alternate, and backup
  • The new port states are forwarding, discarding, and learning
  • The new port types are shared, edge (PortFast), and P2P
  • When an RSTP port receives a legacy BPDU, it reverts back to compatible behavior and performance enhancement benefits are lost
  • BackboneFast is configured on all switches in order to function in STP and UplinkFast is configured on access layer devices

Migrating

  • You are not forced into removing the BackboneFast and UplinkFast commands – if they are left in place, they do not impact the operation of RSTP
  • Removing the Uplinkfast command impacts the bridge priority and port cost values, so be sure you consider this
  • CatOS (FLASHBACK!) does not permit the BackboneFast command within RSTP so you must remove it in that legacy case
  • Plan a phased migration and use a maintenance window as traffic flows can be impacted
  • The configuration of the features such as PortFast, BPDUguard, BPDUfilter, root guard, and loopguard are applicable in rapid-PVST+ mode also

400-101 CCIE R&S Written – Free Resources – STP and other Switch Topics

February 2, 2018 at 8:23 pm

Switching

Here is another edition of our key and free resources for our CCIE RS journey!

2.1.e Implement and troubleshoot EtherChannel
2.1.e [i] LACP, PAgP, manual
2.1.e [ii] Layer 2, layer 3
2.1.e [iii] Load-balancing
2.1.e [iv] Etherchannel misconfiguration guard
2.1.f Implement and troubleshoot spanning-tree
2.1.f [i] PVST+/RPVST+/MST
2.1.f [ii] Switch priority, port priority, path cost, STP timers
2.1.f [iii] port fast, BPDUguard, BPDUfilter
2.1.f [iv] loopguard, rootguard
2.1.g Implement and troubleshoot other LAN switching technologies
2.1.g [i] SPAN, RSPAN, ERSPAN
2.1.h Describe chassis virtualization and aggregation technologies
2.1.h [i] Multichassis
2.1.h [ii] VSS concepts
2.1.h [iii] Alternative to STP
2.1.h [iv] Stackwise
2.1.h [v] Excluding specific platform implementation
2.1.i Describe spanning-tree concepts
2.1.i [i] Compatibility between MST and RSTP
2.1.i [ii] STP dispute, STP bridge assurance

Understanding EtherChannel

STP

Tuning STPTimers

STP BPDU Guard

STP Root Guard

RSTP

SPAN

VSS

Migrating from PVST+ to RSTP

Migrating from PVST+ to MST

Optional STP Features

 

 

 

 

400-101 CCIE R&S Written – Free Resources – Switch Admin and VLANs

January 28, 2018 at 10:37 am

VLANs

Here is the latest installment of resources. This covers the first chunk of the massive Layer 2 section.

2.1 LAN switching technologies
2.1.a Implement and troubleshoot switch administration
2.1.a [i] Managing MAC address table
2.1.a [ii] errdisable recovery
2.1.a [iii] L2 MTU
2.1.b Implement and troubleshoot layer 2 protocols
2.1.b [i] CDP, LLDP
2.1.b [ii] UDLD
2.1.c Implement and troubleshoot VLAN
2.1.c [i] Access ports
2.1.c [ii] VLAN database
2.1.c [iii] Normal, extended VLAN, voice VLAN
2.1.d Implement and troubleshoot trunking
2.1.d [i] VTPv1, VTPv2, VTPv3, VTP pruning
2.1.d [ii] dot1Q
2.1.d [iii] Native VLAN
2.1.d [iv] Manual pruning

LAN Switching

Campus LAN Design Guide

Managing the Switch

errdisable recovery

CDP

UDLD

Configuring VLANs

InterVLAN Routing

VTP

802.1Q

Troubleshooting the 3K

BOOKS

Cisco LAN Switching Fundamentals

 

CCIE RS

 

400-101 CCIE R&S Written – Free Resources – Network Troubleshooting

January 26, 2018 at 2:25 pm

CCIE Resources

Here are more great resources for this section of the CCIE RS written and lab exam!

  • 1.3 Network troubleshooting
    • 1.3.a Use IOS troubleshooting tools
      • 1.3.a [i] debug, conditional debug
      • 1.3.a [ii] ping, traceroute with extended options
      • 1.3.a [iii] Embedded packet capture
      • 1.3.a [iv] Performance monitor
    • 1.3.b Apply troubleshooting methodologies
      • 1.3.b [i] Diagnose the root cause of networking issue [analyze symptoms, identify and describe root cause]
      • 1.3.b [ii] Design and implement valid solutions according to constraints
      • 1.3.b [iii] Verify and monitor resolution
    • 1.3.c Interpret packet capture
      • 1.3.c [i] Using Wireshark trace analyzer
      • 1.3.c [ii] Using IOS embedded packet capture

Important Information on Debug Commands

Extended Ping and Extended Traceroute

Cisco Device Packet Capture

Embedded Packet Capture

Troubleshooting Overview

Catalyst Switch Troubleshooting 

Books:

Troubleshooting IP Routing Protocols

 

CCIE R&S Critical Study Links

January 22, 2018 at 6:00 am

CCIE RS

OK, this post is just as much for me as it is for my readers. I find myself constantly searching for these critical links and I wanted to get them all in one place! Did I miss any? Of course I did – please let me know of your additions by commenting on this post and I will update accordingly!

Exam Topics

https://learningnetwork.cisco.com/community/certifications/ccie_routing_switching/written_exam_v5/exam-topics

Lab Equipment and Software

https://learningnetwork.cisco.com/docs/DOC-22701

Cisco Documentation

https://www.cisco.com/cisco/web/psa/default.html?mode=prod

Reading List

https://learningnetwork.cisco.com/docs/DOC-4601

Studying for the CCIE RS Written and Lab – EIGRP Stub

January 13, 2018 at 12:41 pm

Challenges

In this video, Anthony Sequeira gives a tip on how we should consider preparing for the CCIE written and lab exams simultaneously.