IP Summarization
Hi,
Please advise, I have netowrk
172.16.0.0/16
172.17.0.0/16
172.18.0.0/16
172.19.0.0/16
Could these network summarized as 172.16.0.0/14 ?
I'm going to do a manual summarization on RIPv2 interface.
TQVM in advance.
Please advise, I have netowrk
172.16.0.0/16
172.17.0.0/16
172.18.0.0/16
172.19.0.0/16
Could these network summarized as 172.16.0.0/14 ?
I'm going to do a manual summarization on RIPv2 interface.
TQVM in advance.
Comments
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JVE Member Posts: 76 ■■□□□□□□□□
well 172. is a class B, so really i dont think you will get less then 16 bits with that. You need to work with that third octet -
mikej412 Member Posts: 10,086 ■■■■■■■■■■
kwyap wrote:Could these network summarized as 172.16.0.0/14 ?
Network address 172.16.0.0
Broadcast address 172.19.255.255
And Valid Host Range of 172.16.0.1 - 172.19.255.254
Hum, after a couple of beers and confirming with the TechExams.net IP Subnet Calculator, I'd say the answer is Yes.:mike: Cisco Certifications -- Collect the Entire Set! -
dmaftei Member Posts: 83 ■■□□□□□□□□
mikej412 wrote:...and 1 Subnet with 262142 Hosts.I guess somebody should fix the calculator.
BSEE, MSCS
www.maftei.net -
kwyap Member Posts: 6 ■□□□□□□□□□
Anyone of you have done it before?
When i apply it on the bound interface, a message prompted
"Subnet mask must be greater or equal to the major net"
Theoritically it should work, right? Can anyone explain it? -
EdTheLad Member Posts: 2,111 ■■■■□□□□□□
kwyap wrote:Anyone of you have done it before?
When i apply it on the bound interface, a message prompted
"Subnet mask must be greater or equal to the major net"
Theoritically it should work, right? Can anyone explain it?
Are you sure you changed the rip version to 2?It's just Ripv1 doesnt support cidr, i will check it later in my lab if this isnt the problem.Networking, sometimes i love it, mostly i hate it.Its all about the $$$$ -
JVE Member Posts: 76 ■■□□□□□□□□
I dont think you will ever get that to work. A class B, is the major network address and once you actually type a number like 172, you are forced to have at least 16 bits, no less. That would be like typing the number 10 and putting a 5 bit mask, the router will not accept that. Try a 10.x.x.x and put a mask that has 13 bits and it will work, but you wont get the router to accept a 14 bit mask as a summary route or any other thing with less then 16 bits of a class b address. At least I dont think so.
That calculator saying it is possible or not, I dont think it is right. -
EdTheLad Member Posts: 2,111 ■■■■□□□□□□
JVE, you think wrong, using a mask smaller than the major network is called
supernetting or cidr.Networking, sometimes i love it, mostly i hate it.Its all about the $$$$ -
sprkymrk Member Posts: 4,884 ■■■□□□□□□□
Ed is correct, it does work. My LAN has 2 class C subnets using a 255.255.254.0 mask behind a single router and it works just fine as a supernet. Been running this way with over 400 hosts just fine for a few years.All things are possible, only believe. -
JVE Member Posts: 76 ■■□□□□□□□□
ok, i just been going by examples and I have never seen them give such an example. I have no doubts you guys are right. -
EdTheLad Member Posts: 2,111 ■■■■□□□□□□
kwyap wrote:Anyone of you have done it before?
When i apply it on the bound interface, a message prompted
"Subnet mask must be greater or equal to the major net"
Theoritically it should work, right? Can anyone explain it?
Ripv2 does support cidr but it is not supported with cisco's implementation.
So the message prompt you receive is the correct behaviour.Networking, sometimes i love it, mostly i hate it.Its all about the $$$$ -
sprkymrk Member Posts: 4,884 ■■■□□□□□□□
JVE wrote:ok, i just been going by examples and I have never seen them give such an example. I have no doubts you guys are right.
Just search through a few of my posts and you'll see how many times I have been corrected by folks who know more than me. I have been known to cause a superiority complex in others who hang around me.
All things are possible, only believe. -
BubbaJ Member Posts: 323
ed_the_lad wrote:Ripv2 does support cidr but it is not supported with cisco's implementation.
So the message prompt you receive is the correct behaviour.
Cisco claims that it does:Cisco's implementation of RIP Version 2 supports plain text and MD5 authentication, route summarization, classless interdomain routing (CIDR), and variable-length subnet masks (VLSMs).
I tried this on a 12.3 version and it works fine when setting RIP to version 2 and disabling auto summarization. -
EdTheLad Member Posts: 2,111 ■■■■□□□□□□
BubbaJ wrote:ed_the_lad wrote:Ripv2 does support cidr but it is not supported with cisco's implementation.
So the message prompt you receive is the correct behaviour.
Cisco claims that it does:Cisco's implementation of RIP Version 2 supports plain text and MD5 authentication, route summarization, classless interdomain routing (CIDR), and variable-length subnet masks (VLSMs).
I tried this on a 12.3 version and it works fine when setting RIP to version 2 and disabling auto summarization.
I cant see where in the link you provided it says it supports specifying summarization less than the major net.
Check out summarization restrictions
Rip ios 12.4
I have 12.3(15) and it doesnt work for me.Networking, sometimes i love it, mostly i hate it.Its all about the $$$$ -
!30 Member Posts: 356
I think the answer is :
{ I only find you the sumarize for those 4 segment's } :172.16.0.0/16
172.17.0.0/16
172.18.0.0/16
172.19.0.0/16
You can use this 172 ( I mean first 8 bite's are the same with all IP's segment ).Now let's see how many bite's from the second octect are the same with all four ( and then sum thos 8 + x byte's and get the sumariez ).
16 = 00010000
17 = 00010001
18 = 00010010
19 = 00010011
and get 8+6 mean 14 so the sumariez route is 172.16.0.0/14 .
I think this was helpful !Optimism is an occupational hazard of programming: feedback is the treament. (Kent Beck) -
EdTheLad Member Posts: 2,111 ■■■■□□□□□□
!30 wrote:I think the answer is :
{ I only find you the sumarize for those 4 segment's } :172.16.0.0/16
172.17.0.0/16
172.18.0.0/16
172.19.0.0/16
You can use this 172 ( I mean first 8 bite's are the same with all IP's segment ).Now let's see how many bite's from the second octect are the same with all four ( and then sum thos 8 + x byte's and get the sumariez ).
16 = 00010000
17 = 00010001
18 = 00010010
19 = 00010011
and get 8+6 mean 14 so the sumariez route is 172.16.0.0/14 .
I think this was helpful !Networking, sometimes i love it, mostly i hate it.Its all about the $$$$ -
kwyap Member Posts: 6 ■□□□□□□□□□
Study from BSCI, RIPv2 doesn't support discontiguos network. Is this the reason i couldn't summarise it to 14 bit of subnet mask? -
EdTheLad Member Posts: 2,111 ■■■■□□□□□□
kwyap wrote:Study from BSCI, RIPv2 doesn't support discontiguos network. Is this the reason i couldn't summarise it to 14 bit of subnet mask?
supernet summarization.Networking, sometimes i love it, mostly i hate it.Its all about the $$$$ -
BubbaJ Member Posts: 323
ed_the_lad wrote:BubbaJ wrote:ed_the_lad wrote:Ripv2 does support cidr but it is not supported with cisco's implementation.
So the message prompt you receive is the correct behaviour.
Cisco claims that it does:Cisco's implementation of RIP Version 2 supports plain text and MD5 authentication, route summarization, classless interdomain routing (CIDR), and variable-length subnet masks (VLSMs).
I tried this on a 12.3 version and it works fine when setting RIP to version 2 and disabling auto summarization.
I cant see where in the link you provided it says it supports specifying summarization less than the major net.
Check out summarization restrictions
Rip ios 12.4
I have 12.3(15) and it doesnt work for me. -
mikej412 Member Posts: 10,086 ■■■■■■■■■■
BubbaJ wrote:It says it supports CIDR.
From RFC 2453
supernet routes (routes with a netmask less specific than the "natural" network mask) must not be advertised where they could be misinterpreted by RIP-1 routers.
Looks like it might have been "programmer choice." Probably could have been programed to work in an all Version 2 network.... but changing documention is easier.:mike: Cisco Certifications -- Collect the Entire Set! -
EdTheLad Member Posts: 2,111 ■■■■□□□□□□
BubbaJ wrote:It says it supports CIDR. I will do this again when I have access to my equipment. I'm not where I can try it again. I will try the exact addresses in the original question. I did this with some Class C addresses as a CIDR block.Supernet advertisement (advertising any network prefix less than its classful major network) is not allowed in RIP route summarization, other than advertising a supernet learned in the routing tables. Supernets learned on any interface that is subject to configuration are still learned.
For example, the following summarization is invalid: (invalid supernet summarization)
Router(config)# interface Ethernet 1
Router(config-if)# ip summary-address rip 10.0.0.0 252.0.0.0Networking, sometimes i love it, mostly i hate it.Its all about the $$$$