We help IT Professionals succeed at work.
Get Started

understanding Prefix-List

179 Views
Last Modified: 2017-12-30
I am trying to understand the purpose of the number that comes after the "/".
example:
ip prefix-list TEST seq 5 permit 10.0.0.0/2 ge 17

2 means match 2 bits of first octet 10

however whatever I put , the prefix list will care just about the ge 17

to clarify it I have this table before filtering:

R1(config)#do sh ip route 
      10.0.0.0/8 is variably subnetted, 6 subnets, 6 masks
D        10.1.0.0/16 [90/156160] via 192.168.12.2, 00:00:01, FastEthernet0/0
D        10.2.0.0/17 [90/156160] via 192.168.12.2, 00:00:01, FastEthernet0/0
D        10.3.0.0/18 [90/156160] via 192.168.12.2, 00:00:01, FastEthernet0/0
D        10.4.0.0/19 [90/156160] via 192.168.12.2, 00:00:01, FastEthernet0/0
D        10.5.0.0/20 [90/156160] via 192.168.12.2, 00:00:01, FastEthernet0/0
D        10.6.0.0/21 [90/156160] via 192.168.12.2, 00:00:01, FastEthernet0/0

Open in new window


if I use : ip prefix-list TEST seq 5 permit 10.0.0.0/2 ge 17
router eigrp 1
 distribute-list prefix TEST in


R1(config)#do sh ip route

      10.0.0.0/8 is variably subnetted, 5 subnets, 5 masks
D        10.2.0.0/17 [90/156160] via 192.168.12.2, 00:00:03, FastEthernet0/0
D        10.3.0.0/18 [90/156160] via 192.168.12.2, 00:00:03, FastEthernet0/0
D        10.4.0.0/19 [90/156160] via 192.168.12.2, 00:00:03, FastEthernet0/0
D        10.5.0.0/20 [90/156160] via 192.168.12.2, 00:00:03, FastEthernet0/0
D        10.6.0.0/21 [90/156160] via 192.168.12.2, 00:00:03, FastEthernet0/0

Open in new window


so what 's the purpose of the number that comes after the slash sign "/", example:10.0.0.0/2

Thank you
Comment
Watch Question
Network Security Engineer
Distinguished Expert 2018
Commented:
This problem has been solved!
Unlock 2 Answers and 5 Comments.
See Answers
Why Experts Exchange?

Experts Exchange always has the answer, or at the least points me in the correct direction! It is like having another employee that is extremely experienced.

Jim Murphy
Programmer at Smart IT Solutions

When asked, what has been your best career decision?

Deciding to stick with EE.

Mohamed Asif
Technical Department Head

Being involved with EE helped me to grow personally and professionally.

Carl Webster
CTP, Sr Infrastructure Consultant

An Experts Exchange subscription includes unlimited access to online courses.

Get Started
Ask ANY Question

Connect with Certified Experts to gain insight and support on specific technology challenges including:

  • Troubleshooting
  • Research
  • Professional Opinions
Did You Know?

We've partnered with two important charities to provide clean water and computer science education to those who need it most. READ MORE