sanitize prefix list

[Andriy Sidko]

Hi guys.

for example I have following prefix list:

ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 10 permit 192.168.172.0/28
ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 20 permit 192.168.172.16/28
ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 30 permit 192.168.172.32/29

ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 200 deny 0.0.0.0/0 le 32

if I'd like to merge rules 10,20,30 to one. is list bellow is right?

ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 10 permit 192.168.172.0/26 ge 28 le 29
ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 200 deny 0.0.0.0/0 le 32

Thank you.

[Georg Pauwen]

Hello,

according to my calculation, you need this:

ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 10 permit 192.168.172.0/27
ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 20 permit 192.168.172.32/29

You don't need a deny at the end, it is implicit:

ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 200 deny 0.0.0.0/0 le 32

[paul driver]

Hello

---

@Andriy Sidko wrote:

Hi guys.

for example I have following prefix list:

ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 10 permit 192.168.172.0/28
ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 20 permit 192.168.172.16/28
ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 30 permit 192.168.172.32/29

ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 200 deny 0.0.0.0/0 le 32

if I'd like to merge rules 10,20,30 to one. is list bellow is right?

ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 10 permit 192.168.172.0/26 ge 28 le 29
ip prefix-list PL-DISTRIBUTE-NETS-FROM-GATE seq 200 deny 0.0.0.0/0 le 32

Thank you.

---

Yes it would incorporate your subnets also 192.168.172.0/28 le 29 would allow subnets in 192.168.172.x greater than 28 and less /equal than 29

[Andriy Sidko]

why 192.168.172.0/28 le 29 but not 192.168.172.0/26 ge 28 le 29 

next closest subnet covers all three:

192.168.172.0/28
192.168.172.16/28
192.168.172.32/29

is 192.168.172.0/26 Why why 192.168.172.0/28 le 29 is better?

Thank you.

[sivam siva]

No , In your prefix-list "/28,/29" tells to match only prefixes ,not a subnet mask. when we write prefix-list with "le,ge" that will impact to match subnet mask, so in this prefix-list (10,20,30) nothing to match subnet mask, as georg told we can write this in two line ,listed below.

seq 10 permit 192.168.172.0/27 (this will allow prefix from 172.0 - 172.31)

seq 20 permit 192.168.172.32/29 (this will allow prefix  from 172.32 - 172.39).