Questions tagged [bgp]

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

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When is BGP needed?

I have a question about BGP. When exactly is BGP needed? I remember reading that BGP is needed for communication between autonomous systems, but is this always true? For example, in packet tracer I ...
Artur's user avatar
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18 votes
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In which OSI/TCP-IP model layers do BGP, RIP protocols belong?

We know that in the OSI or TCP-IP model, the higher layer utilizes the services offered by the lower layer. For example, the data link layer uses services offered by the physical layer, network layer ...
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How is BGP "AS_SET" used?

RFC 1771 defines a path attribute type of AS_PATH as follows: AS_PATH (Type Code 2): AS_PATH is a well-known mandatory attribute that is composed of a sequence of AS path segments. Each AS path ...
Eddie's user avatar
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Inbound BGP load-balancing from same ISP router

I have two BGP routers for DIA with an issue with one provider in that the two links to this provider land on the same SP router. My ethernet handoffs via two separate MetroE links from another ...
generalnetworkerror's user avatar
7 votes
1 answer
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BGP authentication-key-chain vs. authentication-key

I found a neat little behavior on a Juniper box I was working with today. We were migrating from a Cisco ASR to an MX and all of our internet exchange peers that had authentication configured didn't ...
Jordan Head's user avatar
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How to understand the output below from BGP?

I don't understand some data of the show route: admin@MX-RE0# run show route 36.250.236.6 inet.0: 736608 destinations, 806660 routes (736608 active, 0 holddown, 7 hidden) + = Active Route, - = Last ...
244boy's user avatar
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3 votes
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Cisco Prefix List Won't Appear in Route Table

I have the following prefix-list configured on our router: ip prefix-list adsvr seq 5 permit 172.30.5.241/32 ip prefix-list adsvr seq 10 permit 134.239.130.143/32 ip prefix-list adsvr seq 15 permit ...
cpatte7372's user avatar
1 vote
1 answer
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BGP Best Path Selection Algorithm

According to this cisco document (https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13753-25.html), shortest AS_PATH is the #4 algorithm in the sequence to evaluate, out of 13 ...
Rafiq's user avatar
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1 answer
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GNS3 Latency test

So I have a small topology ( 4 AS ), and I tested it on a real environment (College Lab) with Cisco routers (2000 series). The latency from one point to another was too high when I used GNS3, the ...
Daniel's user avatar
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33 votes
5 answers
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Better Enterprise Multihoming

I would like to get some opinions regarding ways in which I can improve a BGP dual-provider, dual-router design. Each provider supplies a /24 public subnet. I will refer to the routers, circuits, ...
Dennis Olvany's user avatar
29 votes
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Route servers and looking glasses - what are they?

I've heard the term "route server" and "looking glass" thrown around here. What are they, and why should I care?
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Why use iBGP inside an Autonomous System, if IGP protocols fulfill the need for internal communication

Can anyone explain why we need iBGP for the routes when we have the IGP protocols (OSPF, RIP) for internal communication within the AS? I have read a lot of articles and books, but I could not find ...
user2720323's user avatar
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17 votes
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How to choose a BGP router ID when using IPv6 only?

Usually, when using BGP, you can choose (or your device chooses four you) a router ID from one of your assigned public IP addresses. Now, let's admit you only run IPv6. As the router ID is still a 32 ...
Benjamin A.'s user avatar
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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 ...
SimonJGreen's user avatar
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10 votes
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OSPF or iBGP for interior routing protocol?

So the plan is, two core routers each with a eBGP session to one of two ISPs with full routes. Both routers publish their full tables to each other so they can control traffic flow more intelligently ...
OJS's user avatar
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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 ) " ...
Indu Reddy's user avatar
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1 answer
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Smallest IPv6 block advertised?

We've received a /48 allocation from ARIN, and want to advertise smaller blocks from different sites in our organization. I tried advertising a /56 from each site, but ISP is telling me they won't ...
Ron Trunk's user avatar
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6 votes
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Why do all the intermediary routers need to run iBGP without tunneling?

I'm trying to understand the configuration behind iBGP - I understand you can run full mesh to prevent loops, run confederation or route reflectors, if you don't want full mesh, else run tunneling ...
JuniorPenguin's user avatar
5 votes
4 answers
2k views

eBGP Dual ISP, Dual Edge Router

I am currently using a very simple eBGP and iBGP configuration in my network to route out through a single ISP. This diagram gives a rough idea of what I currently have in operation: I am running out ...
Ethan H.'s user avatar
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How we can assume which network protocol is working in which OSI Layer?

For a long time, I have this kind of silly question: How we can say some network protocols are working in X layer of the OSI model? For example, HTTP working in L7 of OSI, OSPF is L3, ICMP is L4, TCP ...
velpandian's user avatar
5 votes
2 answers
676 views

How does anycast ensure reliable delivery of IP packets for the same IP address on different locations?

With anycast, it would be possible to have the same IP address at multiple locations in the world, without the need of a proxy or VPN that forwards the packets to its final destination. If you would ...
Jomad's user avatar
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5 votes
4 answers
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What is the difference between distance vector protocol and path vector protocol

Can anyone explain me what is the difference between distance vector protocol and path vector protocol. Why we are calling BGP as Path vector protocol . In Best path selection we use the AS_path ...
user2720323's user avatar
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4 votes
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Can I Use BGP as an IGP - Multisite w Redundant Layer 3 MPLS WANs

The requirements are Hundreds of sites. Each has a router and firewall and a switch stack. Layer 3 MPLS WAN with BGP to provider VRF. BGP as an IGP? iBGP Would you distribute a public ASN across all ...
Ronnie Royston's user avatar
4 votes
1 answer
242 views

Prefix hijacked by another ISP

I had the <sarcasm>privilege</sarcasm> for the second time in 10 years to have one of our smaller prefixes hijacked. I have a branch office with a /27 assigned from ISP-A PA space ...
generalnetworkerror's user avatar
3 votes
1 answer
849 views

Can I Announce BGP By Myself? [closed]

I have /24 IP block purchased from APNIC. My ISP is not announcing my ASN. But, they gave me a static public IP that has all ports open. So can I announce my ASN using the live static IP that I have?
Mohit Prajapati's user avatar
3 votes
2 answers
2k views

where to NAT?where to run BGP?

in this diagram : we are peering with 2 ISPs, let's say I have a class c IP space like 200.200.200.0/24 and let's say my ASN is 65000, the thing is where should I run NAT? on which device? I mean on ...
user7741's user avatar
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3 votes
1 answer
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Junos feature to accept multiple BGP paths from multiple peer AS

Cisco IOS provides this hidden BGP command: router bgp <ASN> bgp bestpath as-path multipath-relax It allows the router to install multiple BGP prefixes with distinct as-path'es (but ...
Everton's user avatar
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2 votes
1 answer
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BGP null route when DDoS?

I need suggestion related this issue. We are getting DDoS every two days and its small DDoS last for 5 to 10 min. but sometime its longer in that case we call ISP and they null route specific targeted ...
Satish's user avatar
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Which layers of the protocol stack does a border router access for which purpose?

Dataflows on the internet are often depicted as going from one host via at least two border routers to another host. In these illustrations, the hosts are equipped with and make use of the full ...
zeitweise's user avatar
2 votes
0 answers
7k views

Setup the BGP + ospf network

I've the next Lab with GNS3 I have two autonomous systems(100,200), when the AS 100 run a OSPF with two areas, 0 and 1. The AS 200 has only a router and computer, so easy. But I don't know how to ...
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1 vote
2 answers
166 views

How TCP connections between origin and node servers over a BGP Anycast gets established?

Server A and B have the same IP address with anycast. Server B connects to the origin server that is very close to server A and very far away from server B, since server A is closer, the response will ...
Amin Vakil's user avatar
0 votes
1 answer
1k views

Use ECMP to distribute traffic between two paths, one learned by eBGP and one learned by iBGP on a Cisco NX-OS switch

I maintain two cross-connected switches, R1 and R2, which both have a link to an external switch, R3. R1 and R2 both use eBGP to receive routes to various subnets behind R3. Additionally, R1 and R2 ...
Eric Weber's user avatar
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1 answer
509 views

Regarding ECMP hashing

Assume we have a following topology. R1 represents Router1, R2 represents Router2, R3 represents Router3 and R4 represents Router4. Src represents the source Server. Dest represents the destination. ...
fsociety's user avatar
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