Questions tagged [bgp]
BGP is Border Gateway Protocol, used on the internet both inside of and in between networks.
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Interior vs Exterior Gateway Protocols
I'm new to Networking and I was reading about the Interior and Exterior Gateway Protocols ,but i couldn't understand some points , as stated in a reference:
IGPs are designed to work in private ...
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Is the security of BGP using a pre-shared key dependent on the security of MD5?
The german wikipedia article to BGP states (translated):
In the basic configuration, a BGP-Router is susceptible to spoofig
attacks, through which the attacker can manipulate the routers. By using
an ...
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Allow active connections in firewall on multiple BGP connected routers
We have a network on its own AS with 2 routers connected to 2 AS via BGP (full routes).
The routers also both have a firewall on board that by default drops all traffic, except the one allowed. We ...
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Why are BGP tables suddenly filled with IPv4 routes?
According to article I looked at, bgp routing tables are approaching a maximum size and this is linked to IPv4 exhaustion. Why is this problematic and what is the cause? Will this be a problem with ...
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Why do typical spine-leaf architectures have one border leaf instead of all leafs having an uplink?
In all spine leaf architecture explainers I've seen I've come across the concept of the border leaf which is used as the connection point of the entire clos network to an upstream router, be it either ...
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How Network layer routing actually works in the physical world
This is my first question here, It might be a vague or off topic, I apologise in advance, but I am happy to improve it
Basically I have a somewhat decent theoretical understanding of the OSI model. ...
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BGP outbound traffic engineering in multi-homed network with 2 ISP's
I have network with switches at access layer and 3 host networks, 2 core routers , 2 border routers , that have iBGP connection with each other and ospf with other 2 core routers, also each of them ...
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Can you have multiple paths in BGP through different ASes?
In a course about networks in my university, we learnt about how in BGP routes, each AS chooses a single route to each IP prefix (though you may have multiple iBGP routes).
Meaning that in the ...
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The relationship between IP address and AS number
I've recently been looking for the IP prefixes originating from a specific AS. And there are a few questions I'd like to get confirmed.
We can register IP addresses and ASN from RIR. But where can we ...
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Possibility of transferring data over the same-level networks, rather than the higher-level network
This is a silly(maybe interesting) question.
Assume four ASes are connecting to the Tier 1 network(A, B, C and D). B is peering with C and D. A is close to B, but too far from C and D to make peering. ...
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The relationship between AS upstreams, downstreams and peers
I find AS1221 is both the upstream and the peer of AS13445 from ipinfo.io/AS13445. However, as far as I know, there is no upstream or downstream relationship when talking about peering. Is anything ...
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Are there any ASNs with 0 IP addresses? [duplicate]
Here is the list of all the US ASNs networks ranked by the number of IP addresses: https://ipinfo.io/countries/us
However in the page 10, I can see some ASNs with 0 IP addresses: https://ipinfo.io/...
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how can you establish an (e.g.) IPsec tunnel with Cloudflare, when they announce your IP range via BGP?
I've looked into Cloudflare's "Magic Transit" and I do understand the basic concept of it. However, I do not understand why it would ever work that Cloudflare could return traffic to you (...
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Unable to configure BGP on Arista DCS-7048T-A
I am, admittedly, rather lacking in networking knowledge. However, I managed to learn quite a lot of server and development skills through trial & error and by asking various people/forums. I hope ...
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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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BGP extcommunity extended list
I am just looking at how to use the BGP extcommunity extended list my topology is like below
R1---->R2---->R3
r1 is sending some prefix with soo community 10:...
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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 ...
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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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