The content of this post was generated using ChatGPT, challenging its capacity to bring an accurate technical answer. Asking ChapGTP about network technologies could be fun and useful, it helps me to rediscover things a I didn’t clearly have on top of my mind. I invite you to try on your own.
Differences between iBGP and eBGP protocol
iBGP (Interior Border Gateway Protocol) and eBGP (Exterior Border Gateway Protocol) are both routing protocols used in large-scale networks, but they differ in several important ways.
- Administrative Distance:
The administrative distance for iBGP is 200, while for eBGP it is 20. Administrative distance is the measure of trustworthiness of the routing information, where lower values are preferred. eBGP is considered more trustworthy than iBGP because eBGP peers are typically outside of the local AS (Autonomous System) and have no direct internal connections.
- Hop Count:
iBGP doesn’t change the hop count of a route when it advertises it to its neighbors. On the other hand, eBGP increments the hop count by 1 when it advertises a route to its neighbors. This allows eBGP to influence the path selection process more effectively.
- Route Propagation:
iBGP only propagates routes within the same AS, whereas eBGP propagates routes between different ASes. iBGP peers need to be fully meshed to ensure that all routers are aware of all the routes within the AS, while eBGP peers only need to be connected in a point-to-point manner.
- Next Hop:
iBGP assumes that the next hop for all advertised routes is within the same AS. Therefore, it doesn’t change the next hop information when it advertises a route to its neighbors. eBGP, on the other hand, changes the next hop to its own IP address when it advertises a route to its neighbors. This ensures that the route can be used to reach the destination outside of the AS.
- AS Path:
iBGP doesn’t modify the AS path attribute of a route, while eBGP prepends its own AS number to the AS path attribute when it advertises a route to its neighbors. This allows eBGP to influence the path selection process more effectively, by making certain routes appear longer.
In summary, iBGP is used to distribute routing information within an AS, while eBGP is used to exchange routing information between different ASes. eBGP is more trusted and has a lower administrative distance than iBGP, and can influence the path selection process more effectively by modifying the hop count, next hop, and AS path attributes of the routes it advertises.
In my opinion, this answer was very accurate, It could save a little not repeating the part of iBGP not changing the hops. I give it 90% evaluation. Let me know what you think of it with your comments.
First try: Configuration examples with the differences between iBGP and eBGP protocols
Here’s an example configuration that demonstrates the differences between iBGP and eBGP protocols in a network:
router bgp 65000 neighbor 192.168.1.2 remote-as 65000 neighbor 192.168.1.2 update-source Loopback0 neighbor 192.168.1.2 next-hop-self neighbor 192.168.1.2 route-reflector-client neighbor 192.168.2.2 remote-as 65000 neighbor 192.168.2.2 update-source Loopback0 neighbor 192.168.2.2 next-hop-self address-family ipv4 neighbor 192.168.1.2 activate neighbor 192.168.2.2 activate neighbor 192.168.1.2 send-community extended neighbor 192.168.2.2 send-community extended neighbor 192.168.1.2 route-reflector-client neighbor 192.168.2.2 route-map AS_PATH_FILTER in neighbor 192.168.2.2 prefix-list LOCAL_PREF_FILTER out no auto-summary no synchronization network 10.0.0.0 mask 255.0.0.0 exit-address-family router ospf 1 network 10.0.0.0 0.255.255.255 area 0 exit ip prefix-list LOCAL_PREF_FILTER seq 10 permit 10.0.0.0/8 ip prefix-list LOCAL_PREF_FILTER seq 20 deny any route-map AS_PATH_FILTER permit 10 match as-path 1 ! access-list 1 permit ^$
In this example, we have a router with BGP and OSPF protocols configured. We’re using BGP to exchange routing information with two neighboring routers, one using iBGP and the other using eBGP.
The neighbor at 192.168.1.2 is using iBGP, which means it’s in the same autonomous system (AS) as our router. We configure this neighbor as a route reflector client, which means it’s responsible for reflecting routing updates to other iBGP neighbors. We also set the next-hop attribute to self, which ensures that the router’s IP address is used as the next-hop for routes received from this neighbor.
The neighbor at 192.168.2.2 is using eBGP, which means it’s in a different AS from our router. We use a prefix list to filter outbound traffic to this neighbor, allowing only routes with a 10.0.0.0/8 prefix. We also use a route map to filter inbound traffic from this neighbor, allowing only routes that match a particular AS path.
In the OSPF configuration, we advertise the 10.0.0.0/8 network to other OSPF routers in the same area.
Overall, this example demonstrates how iBGP and eBGP differ in terms of the type of neighbors they connect to and the configuration options available for each type. With iBGP, we can configure route reflectors and use the next-hop-self option, while with eBGP, we can filter traffic using prefix lists and route maps.
This answer wasn’t very accurate, There’s an error in the configuration example regarding the eBGP neighbor, did you see it? I give it 60% evaluation. I gave the feedback and I wen t for a second round. Let me know what you think of it with your comments.
Second try: Configuration examples with the differences between iBGP and eBGP protocols
Here are some examples of how iBGP and eBGP differ in their configuration:
In iBGP (Internal Border Gateway Protocol), routers within the same AS (Autonomous System) are configured to communicate with each other to exchange routing information. iBGP does not care about the physical topology of the network, only the logical topology of the AS. Here is an example of iBGP configuration:
router bgp 100 neighbor 192.168.1.2 remote-as 100 neighbor 192.168.1.2 update-source loopback0 neighbor 192.168.1.2 ebgp-multihop 2
This configuration sets up a neighbor relationship between two routers within the same AS (AS 100). The neighbor’s IP address is 192.168.1.2, and the remote-as command specifies the AS number of the neighbor router, which is also 100 in this example. The update-source command specifies the source IP address for sending BGP updates to the neighbor. In this case, it’s loopback0. The ebgp-multihop command is used when the two routers are not directly connected, and it specifies the number of hops between them.
- eBGP Configuration: In eBGP (External Border Gateway Protocol), routers in different ASes exchange routing information with each other. eBGP cares about the physical topology of the network and requires that the ASes be directly connected to each other. Here’s an example of eBGP configuration:
router bgp 100 neighbor 192.168.2.2 remote-as 200 neighbor 192.168.2.2 update-source loopback0
This configuration sets up a neighbor relationship between two routers in different ASes. The neighbor’s IP address is 192.168.2.2, and the remote-as command specifies the AS number of the neighbor router, which is 200 in this example. The update-source command specifies the source IP address for sending BGP updates to the neighbor. In this case, it’s loopback0.
In summary, iBGP is used for communication within an AS, while eBGP is used for communication between ASes. The configuration of iBGP and eBGP is similar, but the main difference is in how the routers are connected to each other and how the update source is specified.
This answer wasn’t very accurate again, There’s an error in the configuration example regarding the iBGP neighbor now, did you see it? I give it 60% evaluation. Let me know what you think of it with your comments. See you around.
My final evaluation is 40% due to the mistakes in the configuration code used as example. Also, because, I tried to ask for some examples specific to a vendor like Nokia. ChatGPT brought a very generic example that wasn’t too accurate, failing with 0%. It was so bad that I didn’t want it here hahaha. However, I am sure this would get better over the time and I am still amazed how fast you can get info for anything you can ask. Let me know what do you think? Thanks.