Posts in 2013
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BGP Community Attribute
Saturday, May 18, 2013 in Cisco Networking
Community attribute is one of those non-standard BGP attributes that you really need to know well if you wish to use it. The big advantage is that from time to time you will just swoop in and solve a big architecture problem your colleague Network …
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BGP Conditional Advertisements - Advertise Maps
Saturday, May 18, 2013 in Cisco Networking
This is a pretty complex BGP issue because you really need to know the BGP philosophy and maybe even have some basic experience in programming. The trick is to change the behavior of the BGP advertisements depending on the routes that are being …
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BGP Backdoor Route
Sunday, May 05, 2013 in Cisco Networking
When you need to prefer LESS the eBGP route - you need a way to tune it, because not many routing protocols “beat” the eBGPs Administrative Distance (20). The “backdoor” argument sets the routes AD to 200 (like it were an iBGP …
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BGP Route Reflectors
Sunday, May 05, 2013 in Cisco Networking
First of all, why was the concept of Route Reflectors introduced? It´s quite simple actually. If there is no Route Reflector in the iBGP Network - the prefixes are advertised to the first iBGP neighbor, and that’s it, he will not advertise it …
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BGP peer-group
Sunday, May 05, 2013 in Cisco Networking
It’s a simple concept, just a group of neighbors we want to configure with the same group of parameters. It’s defined in 3 steps: 1. Define/Configure the Peer Group ** (config-router)#neighbor CISQUEROS peer-group ** 2. Add the individual …
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BGP Authentication
Sunday, May 05, 2013 in Cisco Networking
It’s configured on PER-NEIGHBOR, or as described in the Previous Post - on the PER-PEER-GROUP basis. ** (config-router)#neighbor CISQUEROS password cisco** From Jeff Doyle’s ROUTING TCP/IP Vol2 (Routing Bible in my opinion, even though I …
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BGP "no sync" and "no auto-summary"
Sunday, May 05, 2013 in Cisco Networking
Two first things that are considered the “BGP configuration best practice” are to disable the SYNCHRONIZATION and disable the Auto Summarization. Why? Auto-summary - to enable the CLASSLESS BGP behavior (config-router)#no auto-summary …
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OSPF Non-Broadcast Multiple-Access (NBMA) Networks
Thursday, May 02, 2013 in Cisco Networking
On the Multipoint Frame-Relay network the default OSPF type is NON-BROADCAST. This means that the OSPF Neighbors will not be formed like on the standard Broadcast Network Segment. Cisqueros_R1#show ip ospf inter s1/0 ** Serial1/0 is up, line …
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OSPF Route Filtering
Thursday, May 02, 2013 in Cisco Networking
First be sure which type of LSA you need to filter by making sure in which part of database the route is: #show ip ospf database [router | network | summary | internal | external] There are 5 ways to perform OSPF Route Filtering: 1. DISTRIBUTE LIST - …
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OSPF Stub Area Types
Thursday, May 02, 2013 in Cisco Networking
First lets make sure we’re comfortable with the LSA types, because you will not understand Stubs before you understand LSAs 100% *LSA - Link State Advertisement, Each LSA has a LSID (Link State ID, like Router-ID for the LSAs) LSA 1 - Router …