Avatar of jskfan
jskfan
Flag for Cyprus asked on

understanding Prefix-List

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
RoutersNetworkingNetwork OperationsNetwork Architecture

Avatar of undefined
Last Comment
jskfan

8/22/2022 - Mon
ASKER CERTIFIED SOLUTION
Hemil Aquino

THIS SOLUTION ONLY AVAILABLE TO MEMBERS.
View this solution by signing up for a free trial.
Members can start a 7-Day free trial and enjoy unlimited access to the platform.
See Pricing Options
Start Free Trial
GET A PERSONALIZED SOLUTION
Ask your own question & get feedback from real experts
Find out why thousands trust the EE community with their toughest problems.
jskfan

ASKER
thanks Hemil Aquino
I had this one :  10.0.0.0/2 ge 17  -----you can see it is just 2 bits after the slash "/"


if it was  10.0.0.0/8 ge 17  or  10.0.0.0/16 ge 17, it would make sense , but  2 bits from the first octet , I could not tell what is covered to be permitted and what  is not...
jskfan

ASKER
i know 10 in binary is 00001010

if  My prefix list is :
ip prefix-list LIST1 permit 10.0.0.0/2

you would think from the first octet (10) in binary it has  2 Zeros 00001010
 so any network that starts with 10 in our case  is permitted

but when I used that prefix list ... the routing table dis not show any of the Network 10
SOLUTION
Predrag Jovic

THIS SOLUTION ONLY AVAILABLE TO MEMBERS.
View this solution by signing up for a free trial.
Members can start a 7-Day free trial and enjoy unlimited access to the platform.
See Pricing Options
Start Free Trial
GET A PERSONALIZED SOLUTION
Ask your own question & get feedback from real experts
Find out why thousands trust the EE community with their toughest problems.
jskfan

ASKER
Thank you Guys !
All of life is about relationships, and EE has made a viirtual community a real community. It lifts everyone's boat
William Peck