Cisco securing device
Switching off unnecessary
no ip source-route ip options drop no ip http server no ip http secure-server no service tcp-small-servers no service udp-small-servers service tcp-keepalives-in service tcp-keepalives-out no ip bootp server no ip finger no ip identd no service config no lldp run no service pad ! add logging buffer logging userinfo logging buffered 50000 ip ssh logging events login block-for 300 attempts 3 within 300
- This automatic time access-list will be created after applying
login block-forcommand
Extended IP access list sl_def_acl
10 deny tcp any any eq telnet log
20 deny tcp any any eq www log
30 deny tcp any any eq 22 log (8015 matches)
40 permit tcp any any eq 22 log
Access Control Lists
How to apply
- First remove ACL from interface
int dialer 0 no ip access-group 90 in exit
- Remove ACL from running-config
Use default statement to delete ACL, then recreate, see below:
default access-list 90 ip access-list standard 90 remark Block abusive IP addresses deny 42.117.7.53 0.0.0.0 deny 123.232.122.162 0.0.0.0 deny 216.38.217.76 0.0.0.0 permit any exit
- Third re apply ACL to interface
int dialer 0 ip access-group 90 in exit
Apply MAC address filtering to Access Point using TFTP
This method is the most secure way to apply multiple ACL lines. This method is nice because the ACL doesn't get updated until after the TFTP is complete, so it should be safe even if the change will interrupt network connectivity. Another safety measure is to schedule a reload. Please follow these steps:
Verify TFTP server is running
Windows machine
netstat -ap UDP | find 69 UDP 0.0.0.0:69 *:* <-- this is expected output
Linux
netstat -ul | grep 69
Schedule a reload
reload in 5 reason Applying ACLs System configuration has been modified. Save? [yes/no]: yes Building configuration... [OK] Reload scheduled for 22:16:38 UTC Sun Nov 24 2013 (in 5 minutes) by dsneteng on vty0 (10.0.99.13) Reload reason: Applying ACLs Proceed with reload? [confirm] *** *** --- SHUTDOWN in 0:05:00 --- ***
Copy ACL to running-config
Copy block-list-apply.txt to tftp root folder. In Windows version of SolarWinds-TFTP-Server its default folder is C:\TFTP-Root.
copy tftp: running-config
Example of block-list-apply.txt file.
! Updated on 24/11/2013@21:00 by user@ ! MAC Vendor Lookup http://www.macvendorlookup.com/list-lookup ! ! Exeption list: ! ! LocationID ! 0022.694C.AABB - Hon Hai Precision - user@ ! ! Apply following to all your APs ! ! interface Dot11Radio0.10 no bridge-group 10 input-address-list 700 exit ! no access-list 700 ! ! LocationID ! access-list 700 deny 0019.7E72.AABB 0000.0000.0000 access-list 700 deny 083E.8E36.CCDD 0000.0000.0000 ! ! Permit all rest ! access-list 700 permit 0000.0000.0000 ffff.ffff.ffff ! interface Dot11Radio0.10 bridge-group 10 input-address-list 700 exit end ! ! MAC filter list has been applied - check for connectivity
Cancel reload
reload cancel *** *** --- SHUTDOWN ABORTED --- ***
Safety cushion by scheduled reload
When applying ACLs or adding extra security it possible to lock out yourself. Therefore before you apply any changes you can schedule reload and do not save running-config to startup-config until you 100% sure all is working correctly. Then cancel scheduled reload and save changes.
- Schedule reload in 5 minutes
reload in 5 Reload scheduled for 19:57:04 GMT Sun Nov 17 2013 (in 5 minutes) by dsneteng on console Reload reason: Reload Command Proceed with reload? [confirm] *** *** --- SHUTDOWN in 0:05:00 --- ***
- Cancel reload
reload cancel *** *** --- SHUTDOWN ABORTED --- ***
- Other options
reload ? at Reload at a specific time/date cancel Cancel pending reload in Reload after a time interval reason Reload reason warm Reload should be warm
- Use copy tftp run when applying ACLs
Then to a copy tftp run to install the updated ACL into the running config. This method is nice because the ACL doesn't get updated until after the TFTP is complete, so it should be safe even if the change will interrupt network connectivity.