Questions tagged [bgp]

BGP is Border Gateway Protocol, used on the internet both inside of and in between networks.

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7 votes
2 answers
3k views

"Local Policy Denied Prefixes" in 'show ip bgp neighbor' output

I've been spending the last week or so troubleshooting some (maybe related, but probably not) issues with Quagga. I have a test router - 7204VXR-NPEG2 running 12.4(24)T6 - with a single BGP session to ...
7 votes
2 answers
37k views

Injecting routes in to BGP for advertisement: BGP network command

I am a complete newbie at BGP configurations.Need some clarification on understanding BGP network command. One of our MPLS site routers have the following config : (Pasting only config snippets ) " ...
10 votes
1 answer
5k views

How would one route an IP network through different ISPs?

So, if I have a site that has 2 (or more) internet connections, with a routable IP subnet that I own, and one ISP goes down, how do I tell the rest of the world to send traffic addressed to my network ...
5 votes
1 answer
3k views

Alcatel-Lucent BGP Default-Originate

I've been looking around trying to find the ALU version of Cisco's "default-originate" but have been unable to find it. Is there a way to generate a zero route towards a BGP neighbor without having ...
6 votes
2 answers
5k views

Impact of IOS BGP soft-reconfiguration-inbound and peering options

This scenario is a network with four routers in a square; each has a connection to a different transit provider with a full BGP table from each. R1----R2 | | | | R3----R4 How do full BGP ...
5 votes
1 answer
13k views

Calculating Cisco router memory requirements for full BGP feeds

This scenario is a network with four routers in a square; each has a connection to a different transit provider with a full BGP table from each. R1----R2 | | | | R3----R4 How do I calculate ...
11 votes
3 answers
805 views

Circular BGP propagation

This one is a difficult to describe, it's hypothetical because I'm learning about routing and right now I'm focused on BGP. Let's say my ASN is 65000, and I announce 192.0.2.0/24. My peer, AS 65001 ...
16 votes
2 answers
11k views

BGP multipath with different ASNs feasible for production networks?

on Cisco (this command is hidden for some reason) #bgp bestpath as-path multipath-relax The default BGP behavior only installs only routes with exact the same AS_PATH into RIB. With multipath-relax, ...
6 votes
2 answers
2k views

forwarding / non forwarding Route Reflector?

I am considering running route reflectors in our current network topology of 20 od MX80's however all current devices are active traffic forwarders. from a scaling perspective RR makes logical sense ...
9 votes
2 answers
512 views

How to handle performance degradation deep in your provider's network?

What are some possible ways to detect packet loss deep in a provider's network that is several hops away? With multiple providers peered over BGP on our Internet edge routers, I need to be able to ...
5 votes
1 answer
6k views

BGP expanded community-list regex

I need to verify that the following regex will match against my criteria, which is: Deny any prefixes beginning with 0: Deny any prefixes beginning with 65000: Deny any prefixes beginning with 0:...
11 votes
1 answer
818 views

How can I check to see if I am receiving MED's?

I have a BGP session with a transit provider in two different cities. We are both using the same AS at both locations. I am expecting them to be sending me MED's for me to use for routing decisions ...
10 votes
4 answers
3k views

Embedded routers vs. software routers in the datacentre

I've been looking for a new 'core' router to put in our new rack which is colo'd at a nearby datacentre. What I've come across is the usual Cisco/Juniper/Brocade lineup, with the usual unattractive ...
17 votes
3 answers
902 views

Is it possible to remotely influence BGP localpref?

A colleague is attempting to implement active/passive internet multihoming. The design entails sending communities (listed below) to the passive provider to lower the local preference at remote ASes ...
15 votes
3 answers
3k views

Why does BGP RR only reflect the best path?

Can anyone answer why does BGP RR only reflect the best path?
0 votes
2 answers
5k views

Advantages to BGP peering over VPN

Given the advantages to be gained by creating a BGP session with a remote AS over a VPN connection (such as traffic ingress and egress control) why are there no providers offering this type of service?...
6 votes
2 answers
3k views

Telefonica Looking Glass?

Is there an openly accessible Looking Glass for Telefonica ? None of the "official" URL's listed hereunder point to a functional Looking Glass server http://www.telefonica-wholesale.com/es/herraIP....
11 votes
2 answers
803 views

BGP Prefix Announcement Issue

I'm having a weird issue. Here is the setup. We have 2 Foundry SX's. SX01 ---> ISPA | | SX02 ---> ISPB I have a /24 from ISPA and another /24 from ISPB. Both /24's are able to be ...
13 votes
1 answer
2k views

What is the maximum prefix size routed in the IPv6 Internet?

In v4, most of the operators filter BGP updates for prefixes longer than a /24, to preserve the size of the full view. What about IPv6 ? Is there such "convention" that stands out ?
10 votes
2 answers
2k views

Why does my Cisco 6509 BGP table use two entries in my TCAM?

I have a problem on my Cisco 6509, each entry in my BGP table occupies two entries in the TCAM. If I show capacity forwarding, I see MPLS entries in L3 forwarding resources. But, I do not use MPLS on ...
11 votes
7 answers
3k views

Only One Path in the Looking Glass

I understand that only the best path is advertised to eBGP neighbors, but is this true of iBGP? If I peer with two providers, I was under the impression that anyone else peering with both of my ...
15 votes
5 answers
2k views

How to filter non-bogon prefixes received via BGP from an Internet Exchange(IXP)?

When connected to an Internet peering exchange(IXP), what is a good way to make sure that people don't send you prefixes that they shouldn't be announcing? With regards to bogons I'm aware of the ...
8 votes
1 answer
2k views

Does RIP to BGP redistribution for an MPLS VPN make sense?

A customer was recently adamant to perform redistribution of their RIPv2 routes into BGP. This is over a standard MPLS VPN solution whereby the CE routers are fully managed. This approach feels ...
7 votes
2 answers
129 views

RPKI in the Enterprise

What is the concensus on the use case for RPKI? Is it useful for a stub AS to perform route validation or is this better left to the providers?

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