Questions tagged [bgp]

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

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IP subnet with extra information outside of BGP and RIPE database

I'm trying to look into the sources of some whois services that can provide more information than BGP and RIPE databases. Example: If I lookup the IP 104.234.88.128 in https://whoer.net/checkwhois I ...
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How to handle route conflict between two routers?

I am learning about route protocols and I would like to know what is the common approach to handle route conflict between two datacenter. I have the scenario bellow: So I want devices on DC1 to ...
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Is BGP always required when you have multiple ISPs?

I am trying to understand when is Border Gateway Protocol needed and I stumbled upon this question: When is BGP needed? The chosen best answer says: You could peer with your service provider and ...
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Can a BGP speaker records alternative paths to the same destination?

The BGP RFC 4271 reads : In the context of this document, we assume that a BGP speaker advertises to its peers only those routes that it uses itself (in this context, a BGP speaker is said to "...
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What are any disadvantages of redistributing eBGP routes into IGP

I wonder if there are any conceptual disadvantages of redistributing routes learned through eBGP peerings into an IGP, like OSPF. I have read of course about performance issues and the risk of ...
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Hot potato routing topology

Im trying understand hot-potato routing better using this diagram that I have made. It shows R1 and R2 in automous system 1 (AS1) are receiving full routes from their parent providers P1 and P2 ...
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How to change the AS number without losing the old BGP configuration?

I use Cisco with IOSv and would like to change AS number without losing the old BGP configuration.How to change the AS number without losing the old BGP configuration?
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iBGP running only between BGP border routers?

I was studying about the BGP protocol and I had this question: Let's say we have an AS having both BGP border routers and internal routers . I know that the border routers should form a full mesh to ...
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Cisco ASA not accepting external traffic without NAT configuration

First of all, I am quite newie in the cisco world, so this could be some easy stuff that I'm missing. My first problem is trying to understand why a Cisco ASA5585 does not show traffic while doing a ...
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In a PE-CE network, we would redistribute routes between BGP and IGP without `bgp redistribute-internal`. How does redistribution works?

In a PE-CE network deployment on Cisco IOS/XE devices like - +-------------+ ...
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eBGP load balancing - why is it not use

I used to think that eBGP does not support load balancing but in Cisco there is the maximum-path parameter that enable ECMP / Fortigate has ebgp-multipath as well so that is obviously not the case ...
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Public IP / IP Transit / IP Peering / ASN / Internet Exchange

I am trying to understand the relationship between IP Transit / Peering and having our range of IP If i subscribed to an ISP internet service and the IP range is allocated by the ISP - it is consider ...
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L3VPN route distinguisher uniqueness

As RD is part of VPNv4 (A.K.A - IPv4 VPN) NLRI and is exchanged between PE routers participating in a L3VPN service. Should RD value be unique only within a given PE router or should it be unique ...
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Is it possible for mobile devices to connect to a far away ASN?

I am trying to understand how the internet connection of mobile devices is done. Knowing that BGP is used for the communication, I would like to know is it possible for the mobile device to connect to ...
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bgp and routing

I need a bit of help understanding what is going on in my topology. I really want to understand why i can ping 1.1.1.1 from r4 but not from r5 or r6. Please help and advise me. Many thanks guys r1 ...
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Why iBGP speaker should not modify next hop address?

I understand the concept of "Split Horizon" that an iBGP router A learns an external route from an iBGP router B, thereafter, iBGP router B will not advertise the same route to other iBGP ...
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Can I announce the same block of /24 given to me by ARIN at two different locations?

The setting: Two locations I'm trying to connect. I have a /24 address block from ARIN Both location have the Same ISP. The Question: Can I announce the same /24 address block at the HQ location to ...
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Cisco BGP Configuration

I need to configure a Cisco C1113 (router B) to enable BGP Routing between two networks. I configured my router B, but I would need to make sure that my configuration is correct... Here is the ...
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How do I view BGP communities of received routes in IOS XE before they go through route-map import policy?

I want to see the communities that are attached to a route when I first receive the route before it goes through the BGP import route-map. In my instance the route-map strips communities off so I ...
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BGP Protocol configuration between two VPC

I would need to configure a cross connect between two VPC networks via SFP Fiber. Unfortunately I'm new on BGP configuration and would need confirmation that I'm doing it on the right way... I have ...
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How does BGP router know the L2 address (MAC address) of the clients?

My situation is that I have 10 Linux servers announcing the same VIP (10.0.0.10 for example) to the router with bird, so the router is doing kind of load balancing with ECMP. ...
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Multi-Home BGP on ASA 5500

We have an ASA that has been doing iBGP for hosted networks. These networks include public address spaces that are routed inside our networks. Recently we have changed providers. The new provider does ...
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Does BGP protocol is required to run IS-IS Segment Routing?

In order to do IS-IS segment routing, do I need to run BGP on routers? Lets say, I have R1-R2-R3-R4 topology. In this topology, I will configure IS-IS segment routing on all routers. My question is do ...
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Traceroute and BGP Next-hop [duplicate]

I just started learning about network engineering and have a very basic question. From my understanding, traceroute shows the routers along the path that the packet needs to traverse through to reach ...
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What would happen if BGP identifier field of both the routers are identical

Say we have two routers R1 and R2. R1 has a router id configured as 1.1.1.1 R2 also has the same router id configured i.e. 1.1.1.1 R1 and R2 are connected to each other via a P2P link. This has an ...
Neil Roy's user avatar
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Limitations of Bilateral peering at an IX

Are there any disadvantages to setting up peering with every other (open) ISP at an IX? All I'm sure is that this could make peering cheaper since the reliance on Tier 1 providers decreases.
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Problem with BGP aggregate-address behavior in IOS when a large number of OSPF routes update all at once

We have a Direct Connect setup to AWS using BGP. We are running a ISR4451 with IOS XE 16.03.06. I have a strange situation where the AWS BGP neighbor drops our connection with the notification: ...
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Summarization on received Routes - BGP

We need to do Summarization on received Routes (as we are receiving 20K+ routes )to reduce load, saving memory, bandwidth, and CPU Cycle. Please suggest some quick and accurate methods to do. I m ...
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In practice, how are BGP Advertisement destinations determined and configured?

Say there is ISP-Alice (ISP-A) and ISP-Bob (ISP-B). They both serve neighboring areas, but they currently only peer with ISP-Charlie. They want to change that and peer directly with each other to ...
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How much RAM you actually need to keep whole global BGP routing table?

It seems that different sources claim very different RAM consumption for having whole BGP routing table information in RAM and having the router to correctly route the traffic. According to ...
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How do two clients of a route reflector learn about each other when no IGP/static-route is used?

I recently learnt that Route reflectors are an efficient alternative to full mesh IBGP peering in a large AS. Imagine a network like: D1 - AS1 <e> R_P <i> RR <i> R_Q <e> AS3 - ...
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How a single BGP-process establishes sessions with neighbours in different VRFs?

In VRF-lite solution scenario, when BGP session is established between CE connected to a VRF in PE. The BGP process or in other words TCP server, is listening on port 179(default) for incoming BGP ...
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Can I assign one of my publicly available IP address to my AWS instance? [closed]

I would like to be able to use one of my publicly accessible ip addresses directly with my aws cloud instance. Is there a way I can assign or transfer one of my ip address to aws? My ARIN registry ...
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BGP <-> OSPF Route Redistribution Loops

In the following topology I have a multi-point redistribution from BGP <-> OSPF and I have recently encountered a routing loop. After further reading I have understood the problematic routers ...
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What is the minimum number of IP addresses an autonomous system can have?

Is it possible to have an autonomous system with just one IP address?
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BMP Server on Cisco [closed]

I'm using router Cisco 2900 series with Cisco IOS 15.4(3) M3, and there is no BMP (BGP Monitoring Protocol) configuration. What should I do? What Cisco IOS version that provide BMP?
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Juniper "show route receive-protocol bgp" output meaning

When you show the received route from a specific neighbor in BGP with a Juniper, the output is the following : show route receive-protocol bgp X.X.X.X inet.0: V destinations, W routes (X active,...
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public ip over private lease line

I have a private cross-connection with a service provider This private connection is connected from my firewall to their router and the L3 IP range /30 for this segment is private However, i just ...
Noob's user avatar
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Valid routes iBGP advertisements

Routers announce to their iBGP peers, the Best routes for each networks it has in its database Is it possible, to announce additionally to the Best route, also all the Valid routes to the iBGP peers ?
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iBGP Question reagrding Distribute - List from EIGRP

So, I have the following topology. A-B | | C-D A-B-C-D are Routers. It doesn't matter what are the IP's of the interfaces. What matters is that I have 2 loopbacks for each router. 1.1.1.1 and 11.11....
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BGP Traffic Engineering - Active\Passive

At my organization we historically would get T1 ISPs at our POPs and take full table + default. BGP would simply "do it's thing" and for the most part everything worked out. There are ...
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Understanding BGP communities

Lets take this basic topology: RTR A ---- RTR B Routers A and B have an eBGP connection. At router B we can have a route map saying: match: community-list xyz action: permit/deny etc Questions: How ...
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How to configure loopback for switch management

We have Cisco Switches (Nexus 93). My PC is on vxlan, in vrf "test" with default gateway 60.254. We want to use loopback 99 for managent for switches. We have created a loopback 99 with an ...
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How to isolate in VRF clients with public IPs in MPLS ISP network

I have OSPF and MPLS enabled in network and run xconnects to transmit L2 traffic. But also have just Internet clients that want public IP addresses. So I configure public IP on interface towards ...
pad19's user avatar
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What determines if a Juniper router is a route reflector client?

When I read bgp router reflector document: You see the topology is this: You see the Router A B C are in one cluster, D E are not clients of it. but how to configure to become this? I compared with ...
244boy's user avatar
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Cisco IOS XR not sending multiple copies of a prefix despite that the additional-path feature is enabled

I have an iBGP session between a Juniper router and a Cisco IOS XR router with add-path/additional-path both in send and receive direction enabled. According to show bgp neighbor, the feature is ...
Martin's user avatar
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BGP route advertised but cannot Ping

I have this rather basic setup with 3 routers running BGP, each has Loopback int configured. Is there an extra step required for R2 to ping R4 Loopback interface despite it's being advertised? R2#sh ...
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BGP-OSPF route injection doesn't work

Background: BGP is fully functional and works as expected so nothing need to worry about, the problem is the route injection between HK_Office <> HK2 and LON1 <> LON_Office, as you could ...
Thomas G. Lau's user avatar
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Why the iBGP's loopback network is not valid in AS?

This is my test topology: this is my Routers' detail configuration: <R1>display current-configuration # sysname R1 # router id 1.1.1.1 # aaa authentication-scheme default authorization-...
244boy's user avatar
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Why the iBGP received network is not valid?

I test the BGP in my PC, this below is the topology: R1--(eBGP)--R2--(iBGP)--R3. and R2-R3-R4 are in OSPF(omit details). this is my detail configuration of BGP: [R1-bgp]dis this # bgp 100 peer 10.1....
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