Layer 2 ASA And OSPF

So recently I had to configure an OSPF adjacency between two routers.

I thought simply permitting multicast traffic to the All Routers and All DR/BDR Routers would permit OSPF Hellos across the link and allow OSPF adjacencies to form. In fact what I saw was routers entering the EXSTART state and the neighbourship failing. I checked the manual, for an OSPF adjacency to form, the following conditions need to be satisfied:

- Area IDs need to match

- Neighbours need to be on the same subnet

- MTUs need to match

- Hello/Dead timers need to match

- Authentication (if any is configured)

So, what I saw was the routers entering the EXSTART state and the neighbourship dropping. Bear in mind, at this point, the only thing permitted through the firewall both ways was multicast traffic to 224.0.0.5 (the AllSPF Routers multicast address) using the OSPF protocol (IP protocol 89). So for some reason the DBD exchange was not taking place.

My initial reaction was to check MTU size. I’d seen a similar issue before where an MTU mismatch (jumbo frames on one side, 1500 bytes on the other side) meant while the non-backbone area’s routes made Continue reading

PBR – Policy Based Routing using Route map

How does the internet work - We know what is networking

About Policy-Based Routing Policy-Based Routing – PBR gives you very simple way of controlling where packets will be forwarded before they enter in the destination-based routing process of the router. It’s a technology that gives you more control over network traffic flow because you will not always want to send certain packets by the obvious […]

PBR – Policy Based Routing using Route map

RFC’s to read for CCIE R&S Lab

As my lab date gets closer I am reading a lot more than I thought I would be, I thought it would be non-stop labbing but I have discovered that I am learning a lot more than I ever thought I would from reading. I have created a page for RFC’s here the list is by […]

The post RFC’s to read for CCIE R&S Lab appeared first on Roger Perkin - Networking Articles.

OSPF &#8211 P-bit Setting in Type-7 LSAs

This post represents the solution and explanation for quiz-5.
It explains one of the Loop Prevention mechanisms in OSPF by using the P-bit in the LSA.

Proxy and Reverse Proxy Server

How does the internet work - We know what is networking

This will be a short Reverse Proxy Caching Overview that will explain what proxy is and what is reverse proxy all about. Normal proxy cache topology is one where the server called proxy server will be some kind of intermediate device between client and server. Proxy will receive all requests from clients and it will […]

Proxy and Reverse Proxy Server

An Introduction to the Nexus 6000

There's a new Nexus in the family, the Nexus 6000. Here are the highlights.

Quiz #6 &#8211 Routing protocols over IPsec

Your company is extending their network with a Remote Office in a different city. You configure an IPsec tunnel between the HeadQuarters and the Remote Office, then you run EIGRP over it, but soon you find out that the tunnel flaps up and down continuously. What is the problem?

PVTD-VR

CCIE Review Questions

I updated the CCIE page to include CCIE Supermemo questions. Please go to CCIE Supermemo Questions. As time progresses I’ll update more and more of these.

EBGP Peering Not Established over a Default Route

This post represents the solution and explanation for quiz-4. The quiz shows that, although the BGP speakers can reach each other, they do not establish an eBGP session. Read more to understand the problem.

Quiz #5 &#8211 OSPFv3 Default Route into a NSSA Area

Your company's network consist of a CORE block running OSPF Area 0 and multiple buildings with 2x distribution switches per building running OSPF NSSA areas.
You have asked your junior colleague to configure OSPFv3 (for IPv6) to match the same design as OSPFv2 (for IPv4), but something goes awfully wrong.

Getting IPv6 Done: A Step-by-Step Framework for Planning an IPv6 Deployment

TCP Handshakes, Routing, Hairpinning – Oh My!

TCP Handshakes, Routing, Hairpinning – Oh My!

TCP Handshakes, Routing, Hairpinning – Oh My!

Baby Bro, Part 3: Containers and Loops

• tables
• sets
• vectors
• records

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event bro_init()
    {   
    local letters = table([1] = "a", [2] = "b", [3] = "c");
    print letters;
    }   

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event bro_init()
    {
    local letters = table([1] = "a", [2] = "b", [3] = "c");
    
    for (key in letters)
        {
        print letters[key];
        }
    }

Find link errors with op script

Find link errors with op script

Find link errors with op script

NAT &#8211 Port Forwarding in Both Directions

This post represents the solution and explanation for quiz-3.
NAT on Cisco IOS can be pretty frustrating sometimes and it may take time and practice to master it.