Cisco CCNP BCSI Exam Tutorial Configuring EIGRP Packet Authentication
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Cisco CCNP/BCSI Exam Guide: Configuring EIGRP Packet Authentication
Overview
Mastering EIGRP authentication is crucial for passing the BSCI and CCNP exams. Let's dive into the process with insights from Chris Bryant, CCIE
12933.
Key Concepts
Configuring RIPv2 and EIGRP authentication using key chains can seem daunting due to the complex syntax. However, mastering this skill is essential for success in CCNP exams.
Previously, we explored RIPv2 packet authentication using clear-text and MD5. EIGRP authentication is similar, with both text and MD5 options available, but EIGRP's commands require more detail.
It's important that EIGRP neighbors agree on the authentication mode. Mismatched modes between routers?"like one using MD5 and the other text?"will cause the adjacency to fail, even if the passwords match.
Configuration Steps
We will configure EIGRP authentication on an Ethernet segment. Here’s how to set up a key chain called "EIGRP" on two routers, using key number 1 and the key-string "BSCI."
On Router R2
```plaintext
R2(config)
key chain EIGRP
R2(config-keychain)key 1
R2(config-keychain-key)key-string BSCI
```Check your configuration with:
```plaintext
R2
show key chain
```On Router R3
```plaintext
R3(config)
key chain EIGRP
R3(config-keychain)key 1
R3(config-keychain-key)key-string BSCI
```Verify with:
```plaintext
R3
show key chain
```Both routers should display the key and its attributes, showing they're always valid.
Applying the Key Chain
The EIGRP command syntax can be tricky: the protocol and AS number are placed in the middle of the command line, and two commands are required.
On Router R2
```plaintext
R2(config)
interface ethernet0
R2(config-if)ip authentication key-chain eigrp 100 EIGRP
R2(config-if)ip authentication mode eigrp 100 md5
```You might see the following message when the adjacency is momentarily disrupted:
```plaintext
%DUAL-5-NBRCHANGE: IP-EIGRP 100: Neighbor 172.12.23.3 (Ethernet0) is down: keychain changed
```
On Router R3
```plaintext
R3(config)
interface ethernet0
R3(config-if)ip authentication key-chain eigrp 100 EIGRP
R3(config-if)ip authentication mode eigrp 100 md5
```When the configuration is correct on both sides, the adjacency should reestablish itself, indicated by the message:
```plaintext
%DUAL-5-NBRCHANGE: IP-EIGRP 100: Neighbor 172.12.23.2 (Ethernet0) is up
```
Verification
Always verify the status with:
```plaintext
show ip eigrp neighbor
```
By practicing EIGRP key chains on your lab equipment, you'll be well-prepared for the BSCI exam. This hands-on experience is invaluable!
You can find the original non-AI version of this article here: Cisco CCNP BCSI Exam Tutorial Configuring EIGRP Packet Authentication.
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