Questions tagged [bgp]

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

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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 ...
6 votes
2 answers
17k views

Local pref VS prepend AS-path for two eBGP router

I have two routers, AS50 and AS100, both are under my control. Since they are using different ASN, they should be eBGP routers. These two routers are connected by internet VPN and lease line, which ...
1 vote
0 answers
876 views

BGP transitive attributes for single ASN multiple prefixes multiple neighbors

I believe I'm on the right track, but have stumble across something with advertising BGP prefixes to neighbors. I am wonder how if I have a single ASN with multiple prefixes (99.1.1.0/24 and 111.1.1.0/...
1 vote
2 answers
91 views

Are eBGP networks automatically advertised to iBGP?

as the title says, I am working with a rather simple topology: R1<--eBGP-->R2<--iBGP-->R3 R1 has an eBGP neighborship with R2. I recently added an iBGP session between R2 and R3 (both are ...
2 votes
0 answers
354 views

ip routing preference problem

On my Huawei CE12800 device, I am trying to run this config. Beside a standart BGP process, I am using three community values to control traffic with my upstream provider. With 555 community value, I ...
1 vote
0 answers
176 views

Is there a way to check which routes are matched by a term in a routing map?

I have created a prefix-list and I am using it in a route-map. However, my route-map is not working as I expect it to work. ip prefix-list LIST_A seq 5 permit 10.20.20.0/22 ge 32 route-map A-B-OUT ...
2 votes
0 answers
806 views

How to redistribute BGP routes learned from AWS in one VR into another BGP running in another VR in Palo Alto firewall?

I have about 1000+ prefixes I am learning from AWS on Palo Alto through a BGP. This is on the secondary VR. Main VR is where my core routing is situated along with another BGP instance pointing to ...
1 vote
0 answers
67 views

Redirect Junos IP public -> IP private

we have an MX204 here that works as our BGP, border router and it is gateway of a service that has private IP, I need to access this service with private IP outside our network, you can tell me if I ...
1 vote
1 answer
65 views

BGP: Are Virtual Internet Exchanges more efficient than normal internet transit?

There are a number of virtual internet exchanges that BGP peer over VPN links when local presence is not available. Given the IP encapsulation overhead, and the fact that these routes still cross the ...
1 vote
1 answer
104 views

cisco BGP command: network without mask

My topo is as follows, following is my configuration, although bgp command network is without mask, it could advertise classful address 10.0.0.0 R1#show ip route Codes: L - local, C - connected, S - ...
2 votes
2 answers
187 views

Method to rename the existing BGP peer group

In Cisco ASR router, do we have any method to rename the existing peer group without removing and recreating it?
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1 answer
77 views

Does an official list of tier 1 ISPs exist?

I'm trying to find an official list of tier 1 ISPs. I found a list on Wikipedia but can't quite understand how it was compiled, it just lists AS rank as a source. I also found some other websites that ...
0 votes
1 answer
59 views

How can I have multiple servers and IPs if I only have 1 ip with gigabit connection?

I have 1 gigabit connection with static public IP address... Without depending on my local ISPs colaboration, is it possible to buy IPs from an online service and route each individual IP to my local ...
1 vote
1 answer
201 views

How can I implement BGP between two routers that have already been configured with different routing protocols?

I have two different AS with different IP ranges and subnets, and the first router stack is running RIP, and the second one is OSPF. I want to configure BGP between "Router-PT Router23" and &...
0 votes
1 answer
64 views

BGP configuration multi-hop ping not working

I'm learning bgp and studying on a simple lab I'm unable to ping a loop0 two hops away while the loop0 on the nex-hop router is reachable Topology is simple R3-R1-R2, from R2 i'm able to ping loop0 on ...
0 votes
1 answer
39 views

How to determine a BGP node's IP address

Let's say you do a traceroute scan to a network that is far away, and there a lot of intermediate hops, how do you know which one belongs to a BGP node, and which one is part of the target server? Let'...
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57 views

How to understand BGP Announcements on Cloudflare Radar?

See the "BGP Announcements" card on any AS page. Example: https://radar.cloudflare.com/routing/AS13335 I fail to reproduce the same numbers with my own tool when I use a single location from ...
0 votes
2 answers
100 views

How can we use "source port randomization" in BGP?

I wonder if we can change the default port TCP port number(179) used during the BGP session. I recently came across a document BGP Vulnerability Testing: Separating Fact from FUD. It suggested ...
0 votes
0 answers
41 views

Why CDN ASes are not shown in BGPreader?

I am using bgpreader as bgpreader -A "20940" -w 2023-7-28,2023-7-31 where ASN 20940 is Akamai (a CDN). I wanted to view RIB, updates involving this ASN. I couldn't find the result for other ...
1 vote
1 answer
215 views

Juniper - ECMP with BGP

As I know, with the command "multipath" BGP can install more than 1 route to a specific destination into the routing table. IE.: 1.1.1.1 --> 192.168.0.2 1.1.1.1 --> 192.168.0.5 But ...
1 vote
1 answer
55 views

BGP Convergence Design Question

i read that good convergence method for BGP is to rely on IGP Convergence by declaring next-hop dead and not decreasing BGP timers because the latter will cause unstable network. i really fail to see ...
0 votes
1 answer
78 views

Difference between internet path and AS path

As per my understanding, the Internet is the interconnection of ASes where BGP is a kind of "glue". BGP carries routing information from one AS to another. Also, the AS path is one of the ...
0 votes
2 answers
148 views

What is benefit of allocating ASN to edge routers and not Ip addresses

What is benefit of allocating ASN to edge routers and not Ip addresses ? I mean we could have given these edge routers unique public ip addresses too ?
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1 answer
118 views

Can control plane and data plane be different in BGP?

I have heard that the BGP routes exchanged between the routers do not necessarily mean that the actual data path will follow the specified routes. How can the data path and control path be different ...
0 votes
1 answer
124 views

The Use of BGP Communities

I am studying BGP communities at the moment. I understand that communities are path attributes which are a way of tagging specific BGP route advertisements in order to ensure proper route selection ...
24 votes
7 answers
58k views

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 ...
0 votes
2 answers
67 views

Advertising IP prefixes to the internet using BGP

I am studying BGP at the moment. From what I've learned, in order to participate in routing on the internet and use BGP, we need to register a public provider-independent IP address block and a public ...
0 votes
0 answers
72 views

The Atomic Aggregate Attribute in BGP

I am trying to understand how the Atomic Aggregate attribute works in BGP. So if my understanding is correct, once we configure route summarization, the path attributes of those routes that we've ...
0 votes
1 answer
81 views

iBGP Confusion - Clarification Needed

Sorry if this is an XY problem -- struggling to understand a few concepts. To put it simply, I just don't understand when iBGP is needed. Been reading the CCNP Enterprise - Core and the example ...
0 votes
1 answer
325 views

MED versus AS Path Prepending for inbound path manipulation

I am currently studying about the BGP path selection process and I came across MED and AS Path Prepending which can both be used to affect how traffic enters our network. Are there any scenarios where ...
0 votes
1 answer
54 views

Confused about the BGP ConnectRetryTimer

I am studying about BGP adjacencies at the moment. About the Idle state. I've read from my Cisco book that errors can cause the neighbor state to revert back to Idle and the ConnectRetryTimer is set ...
0 votes
1 answer
108 views

Traffic Flow From the Customer Through the ISP

I am currently learning about BGP at the moment and I have a question about the traffic flow and redistribution. So ISPs typically run some sort of IGP within their AS. If I was to send a packet to ...
0 votes
2 answers
68 views

How do ISPs ensure that the IP block that is being advertised to them is valid?

Consider the following situation where we have a customer that is connected to two ISPs for redundancy Let's say that this customer has its own IP address space that it wants to advertise to those ...
1 vote
2 answers
113 views

BGP and Multi-Hop Adjacencies Using TCP

I am studying the basics of BGP and my book states the following: "BGP sessions use TCP port 179. TCP allows for adjacencies that are multiple hops away" I understand that this allows ...
0 votes
1 answer
129 views

What is the use of private ASNs?

I am currently studying BGP at the moment. The public ASNs that are assigned to ISPs and larger organizations that want to participate in routing on the internet make perfect sense to me. However, I'...
3 votes
1 answer
93 views

BGP: What are the considerations for announcing a RIPE block in ARIN-controlled territory?

We have an ASN and are considering leasing a addresses under RIPE's jurisdiction (because they cost less). However, we are in North America and would announce those addresses via BGP to our providers ...
1 vote
1 answer
54 views

EIGRP AS versus BGP AS

I am currently studying the basics of BGP and I am very early into this topic. So with EIGRP, I was told that an AS is basically a collection of routers/a routing domain that is under a single ...
0 votes
1 answer
336 views

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 ...
0 votes
1 answer
162 views

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 ...
0 votes
1 answer
52 views

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 ...
0 votes
1 answer
73 views

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 ...
2 votes
1 answer
609 views

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 ...
3 votes
2 answers
2k views

How to block advertisement of a prefixes recieved from 1 BGP neighbor to another

I have a eBGP topology as follows: RTR1 ------ DUT ------ RTR2 (AS100) (AS200) (AS300) I do not want any routes sent by RTR1 to be advertised into RTR2 by DUT I do not know what exactly the ...
1 vote
2 answers
491 views

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. ...
0 votes
2 answers
140 views

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 ...
0 votes
3 answers
490 views

IGP between 2 routers with an uncooperative router in the middle

I've got two routers, A and B. A gets some routes over BGP over a VPN connection, and has a leg on 10.0.0.0/24. It also can access the whole 10.0.0.0/16 via its default gateway. B is on 192.168.0.0/...
0 votes
1 answer
113 views

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 ...
0 votes
1 answer
385 views

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 ...
0 votes
2 answers
78 views

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. ...
0 votes
2 answers
413 views

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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