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</details>
**This page was copied from** [**https://medium.com/@in9uz/cisco-nightmare-pentesting-cisco-networks-like-a-devil-f4032eb437b9**](https://medium.com/@in9uz/cisco-nightmare-pentesting-cisco-networks-like-a-devil-f4032eb437b9)****
**EIGRP (Enhanced Interior Gateway Routing Protocol)** is a dynamic routing protocol. **It is a distance-vector protocol.****If there is no authentication and configuration of passive interfaces, an intruder can interfere with EIGRP routing and cause routing tables poisoning.****Moreover, EIGRP network (in other words, autonomous system) is flat and has no segmentation into any zones.** What could this mean for an attacker? Well, if he injects a route, it is likely that this route will spread throughout the autonomous EIGRP system.
First and foremost, attacking a standalone EIGRP system requires establishing a neighborhood with a legitimate EIGRP router, which opens up a lot of possibilities, from basic reconnaissance to various injections.
For this I will use [**FRRouting**](https://frrouting.org/). This is an open-source software which is designed to create a router in Unix and Linux. **FRRouting** allows you to implement **a virtual router that supports BGP, OSPF, EIGRP, RIP and other protocols.** All you need to do is deploy it on your attacker’s system and you can actually pretend to be a legitimate router in the routing domain. I’ll show you how to deploy FRR on your system in the next section.
**Connecting to the routing domain allows us to do enumeration and reconnaissance of networks and not spend a lot of time scanning.** This method saves you a lot of precious time. **Plus, by scanning, you can get burned in front of IPS/IDS security systems.** To me, connecting to the domain and enumeration is the attack vector on routing domains that gives you the most impact. But to do this you need to deploy **FRRouting**. Here we go.
**It is necessary to edit the configuration file daemons.** It contains the configurations of the daemons in the context of their activity. Either they are enabled (yes) or not (no). We need to activate the **eigrpd** daemon.
After that, you need to correct the **vtysh.conf** file by adding a line responsible for saving the configuration to one file, so that configurations of different protocols are not scattered into different files **(e.g. eigrpd.conf, staticd.conf).** It is configurable optionally.
```
~# nano /etc/frr/vtysh.conf
service integrated-vtysh-config
```
The FRRouting configuration is done. Now it’s time to run the FRR daemon. **And yes, we need to enable traffic routing. By default it is disabled in Linux distributions**
> **However, don’t forget that the EIGRP routing domain can be protected by authentication. But you still have a chance to connect to the routing domain. When hello packets are sent out, they also contain cryptographic hashes. If you can extract these hashes from the traffic dump and reset the password, you can log on to the routing domain with this password.**
Go to global configuration mode and start the **EIGRP** process, specify the autonomous system number — **1**
And we also need to declare the network we are in. We are at 10.10.100.0/24. My address is 10.10.100.50/32
During the establishment and maintenance of the neighborhood between EIGRP routers, routers exchange their routing information. After the neighborhood is established, new routes will appear in our routing table of the attacking system, namely:
Thus, after establishing the neighborhood, we know about the existence of these subnets, which makes it easier for us to pentest and save time. We can do without additional subnet scanning. Now we are in the EIGRP routing domain and we can develop some attack vectors. Let’s talk about them.
**I have found that generating and quickly sending out mass EIGRP hello packets overloads the router’s CPU, which in turn can open the door to a DoS attack.** I have developed a little [**helloflooding.py**](https://github.com/in9uz/EIGRPWN/blob/main/helloflooding.py) **** script, but it seems to me that the script lacks the speed of sending out the packets. **It’s caused by GIL**, which prevents the **sprayhello** function from running in multiple threads per second. **Eventually I’ll rewrite the script in C.**
The essence of this attack is a simple injection of a false route that will poison the routing table. Traffic to, **say, the**`10.10.100.0/24`**network will go nowhere, causing a denial of service. Such an attack is called a Blackhole.** The script [**routeinject.py**](https://github.com/in9uz/EIGRPWN/blob/main/routeinject.py) **** will be the tool used to perform it. For this example, I will send traffic destined for host `172.16.100.140/32` to the black hole.
To establish EIGRP neighbors, **routers use special K-values.** They must be the same among all EIGRP neighbors. If at least one K-value does not match, the EIGRP domain will crash and the neighborhood will be broken. We will use [**relationshipnightmare.py**](https://github.com/in9uz/EIGRPWN/blob/main/relationshipnightmare.py) **** to perform this attack**.**
**On behalf of the specified IP and will be sent an inject on the multicast EIGRP IP address, in which the K-values are different.** In my case, I will break the neighborhood on behalf of router GW1 **(address is 10.10.100.100)**.
**A DoS attack can be carried out in this way. During operation, endless breakups and neighborhood attempts occur, paralyzing part of the EIGRP routing domain.**
The essence of this attack is to provoke the sending of a huge number of false routes, which will overflow the routing table. This depletes the computing resources of the router, namely the CPU and RAM, since the injections occur at enormous speed. This attack is implemented [**routingtableoverflow.py**](https://github.com/in9uz/EIGRPWN/blob/main/routingtableoverflow.py) **script**
After running the script, the routing table starts overflowing with routes. The random addresses of the target networks are due to the use of **RandIP()** in [**Scapy**](https://github.com/secdev/scapy).
<summary><strong>Support HackTricks and get benefits!</strong></summary>
* Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
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* Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
* **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.**
* **Share your hacking tricks by submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**
