1. MM Clements Adding Value to IOS Configs

2. Introduction IOS configs need you to add information Basic IP and subnet mask Clock rates for serial links Routing protocol statements Access control lists But…. There are added extras that will make a configuration better 2 ITCN

3. Comments in configuration files A config file can be confusing if you are asked to maintain or adjust an existing configuration Suppose you are asked to change the clock rate on the link to our Paris router Simple? Sure Let’s have a look….. 3 ITCN

4. Here’s the Config… interface Serial0/0 ip address 172.16.0.2 255.255.255.252 clock rate 64000 ! interface Serial0/1 ip address 172.16.0.13 255.255.255.252 clock rate 64000 ! interface Serial0/2 ip address 172.16.0.10 255.255.255.252 clock rate 64000 Which Serial interface links to Paris? 4 ITCN

5. What now? We need more information, so we can… Ask your supervisor? Phone Paris? Check documentation? Check with a colleague? Guess? 5 ITCN

6. Improving the config We could add a description in the config file This has no effect on the operation of the router It has a great effect on the human side of our operation It allows us to add some human-type data to the machine configuration 6 ITCN

7. How it is done… Medway#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Medway(config)#interface s0/0 Medway(config-if)#description Link to Paris Medway(config-if)#exit 7 ITCN

8. Appears as….. ! interface Serial0/0 description Link to Paris ip address 172.16.0.2 255.255.255.252 ! 8 ITCN

9. Much clearer with comments This has made repeat operations much easier This is not rocket science but adds a good measure of sense to our configuration 9 ITCN

10. Challenge number 2 You have been asked to change the subnet mask on the second floor LAN Easy? Of course Let’s have a look at the config file... ITCN 10

11. The config file interface FastEthernet0/0 ip address 192.168.1.1 255.255.255.224 duplex auto speed auto ! interface FastEthernet0/1 ip address 192.168.11.1 255.255.255.224 duplex auto speed auto ITCN 11 Which interface?

12. Can’t get on with the job yet because We need more information, so we can… Ask your supervisor? Phone the second floor? Check documentation? Check with a colleague? Guess? ITCN 12

13. The solution... Avery_Hill#conf t Enter configuration commands, one per line. End with CNTL/Z. Avery_Hill(config)#int fa0/0 Avery_Hill(config-if)#description Second Floor Office ITCN 13

14. Appears as interface FastEthernet0/0 description Second Floor Office ip address 192.168.1.1 255.255.255.224 duplex auto speed auto ! interface FastEthernet0/1 description First Floor Office ip address 192.168.11.1 255.255.255.224 duplex auto speed auto ITCN 14

15. Solved – now another You are asked to change the security in a network and need to adjust an Access Control List Jones’ is no longer allowed access to the Internet Let’s see the config first ITCN 15

16. Remarks Remarks about entries in an IP access list make the list easier to understand and scan. For example, it is not immediately clear what the purpose of the following entry is: access-list 1 permit 171.69.2.88 ITCN 16

17. Adding Remarks to ACLs It is much easier to read a remark about the entry to understand its effect, as follows: access-list 1 remark Permit only Jones workstation through access-list 1 permit 171.69.2.88 ITCN 17

18. Easing our work The remark made it easy to understand the purpose of the ACL statement Can add one comment per line access-list 1 remark comment top line access-list 1 permit host 192.168.1.10 access-list 1 remark comment next line access-list 1 deny host 192.168.1.144 ITCN 18

19. Other additions Encrypted enable password TELNET logins and passwords Always use ‘cisco’ or ‘class’ for passwording in exercises NEVER use these in a production network ITCN 19

20. Conclusion Comments make human lives easier It facilitates maintenance It increases accuracy Passwords increase security Messages allow us to see where we are logging into ITCN 20

21. References [1] http://www.cisco.com/en/US/docs/ios/12_0t/12_0t2/feature/guide/comment.html ITCN 21