Class A Subnet

I have two new Xserve RAIDs and was configuring the network settings. I found that I could not enter a manual IP address with a 255.0.0.0 subnet. When I called support they said it was because the fiber channel was using a class A, so I had to use a different subnet. So is this true? What are the workarounds? Obviously I cannot change my subnet just for these 2 devices.
Thanks for any clarification on this.

Hi Jeff,
The fibre channel definitely isn't eliminating use of the entire 255.x.x.x class A. We are using a subnet mask of 255.255.255.0 on both of our RAIDs. And according to Apple's Xsan manual, you should be able to use the 255.0.0.0 subnet.
http://manuals.info.apple.com/en/xsan/XsanGettingStarted.pdf
See pg 17 in the guide:
I am assuming you are using the same subnet on your other network devices and it matches your available IP range, but you might want to double-check the sub on one of the other devices and make sure . If you are successfully using the 255.0.0.0 sub on your other devices, try reseating the controllers in the RAIDs (you need to power them off to do this) and then see if it lets you configure with that sub.
-Phoenix

Similar Messages

No support for Class A subnet?

We have a firewall and are using the 10.x.x.x class A domain. However I can not set the subnet mask for the RAID to 255.0.0.0. The best I can get is class B 255.255.0.0. Has anyone else been able to get a class A subnet on their RAID?

It appears that it's not possible to configure Xserve RAID network interfaces with a 10 network address and class A (255.0.0.0) subnet or a 10.254 network address and class B subnet (255.255.0.0). These configurations seem to reserved. I seem to recall this being documented somewhere, but I now can't find it. If anyone can find a link to this, maybe they could post it.

DHCP - Two Class C Subnets

Our OS X (10.4.11) server is not handing out ip addresses via DHCP. The server is set to hand out ip addresses from a second Class C subnet that has been added to the router. No clients are ever listed and remains at 0.
Perhaps it has something to do with the new AirPort Extreme base stations. How do you turn off "distribute IP addresses"?
Could something be set wrong in the DNS service that is causing this?
Does something else need to be done in the router so that both subnets are recognized?
I would appreciate it if someone could steer me to a helpful site.
This has successfully been done at two different locations here with older base stations and on networks that have only the main Class C network.
Thanks for any help.

IIRC, the server will start handing out IP addresses from the lowest number and work up.
Therefore I wouldn't expect the second /24 network to be used until 254 IP addresses have already been used in the first /24.
In other words, the second /24 network is used as an overflow.
The server does have its own IP address in the second /24 network, right? I haven't ever tried handing out DHCP addresses for a subnet that the server doesn't have a leg in.

Wrt160n v3 - Class B Subnet mask

I'm trying to set my router IP to a class B network (172.16.20.x) but the web UI only shows class A subnet masks.. how do I set my subnet mask to 255.255.0.0?
I need to do this so I can use this wireless router as an access point in an existing network.
Thanks in advance.

You can only set subnet mask 255.255.255.0 or smaller on the WRT. It's a consumer router and designed to be used as router in a consumer environment.
If you only use it as access point your LAN with a larger mask you have to choose the IP address which suits you best for configuration purposes.
You wrote you have a network 172.16.20.* but then you write you have subnet mask 255.255.0.0. What is the case? If you only use 172.16.20.* then you should use subnet mask 255.255.255.0 instead. Otherwise, with 255.255.0.0 your LAN would be 172.16.*.*. What do you really use?
If it's 255.255.0.0 you have to pick an IP address for the WRT which works best with the computer most likely to configure the WRT. For instance, if your computer has the IP address 172.16.20.10 and that's the computer you usually use to configure the WRT then set an IP address 172.16.20.* as LAN IP address and set subnet mask 255.255.255.0. With these settings all computers with IP address 172.16.20.* are able to access the web interface. All computers with other IP address won't be able to access the web interface without changing the IP address first.
But this only affect access to the web interface. Wireless connectivity of wireless clients to the LAN is fully independent from whether a client can access the web interface or not.

Class C subnet challenge

Given a class C address of 192.168.25.0 / 24, I need to design a network address scheme for 4 subnetworks where the zero subnet is used and the number of hosts on subnet A is 2, Subnet B is 5, Subnet C is between 20 and 30 and subnet D is between 75-100. I'm stumped because if I use a /26 mask then I won't have enough host for subnet D. If I use a /25 mask then I don't have enough subnets. Clearly I am missing something in this simple problem and help will be most appreciated. VLSM is not being used or allowed.
Walt

Hi Walt,
Diving subnet equally will not ensure all subnet to be served as per your requirement. I think below is the only one as per
your requirement....or you can have one more supernet to cate this requirement
Subnet A: 192.168.25.0/30
Subnet B: 192.168.25.8/29
Subnet C: 192.168.25.32/27
Subnet D: 192.168.25.128/25
Regards
Mahesh

Using both Dynamic and Static NAT with two Different Internet facing Subnets

We have two Class C Public Address subnets. We started with Subnet (A) and have many of our Internet accessible devices on it. It is running on a Cisco PIX 515R. We bought a new ASA 5510 8.3(2) and started Migrating the Users and new servers to it so I started with our second Class C Subnet (B). Later on down the road I found out that if the Firewalls Default Gateway is is set to a (B) Interface subnet, then the servers that are statically mapped to a (A) Address will have a (B) address when they communicate out to the internet. So they are receiving packets on their (A) Address, though replying to them with a (B) address.
It was mentioned that I should be able to combine static and dynamic NAT mapping to allow devices behind the firewall to have a fixed external Address when communicating outbound as well as inbound.
So For instance I want the Following: when the Internal Replies I want the reply to come from the mapped IP, not a IP from the Dynamic Pool.
Public IP: 192.168.1.100/24
Internal IP: 10.0.0.100/16
Public IP: 192.168.5.101/24
Internal IP: 10.0.0.101/16
interface Ethernet0/0
description 192.168.1.0/24 Network Outside IP
nameif outside-1
security-level 0
ip address 192.168.1.1 255.255.255.0
interface Ethernet0/1
description 192.168.5.0/24 Network Outside IP
nameif outside-5
security-level 0
ip address 192.168.5.1 255.255.255.0
interface Ethernet0/2
description inside 10.0.0.0/16
nameif inside
security-level 100
ip address 10.0.0.1 255.255.0.0
object network serverA_o
host 192.168.1.100
object network serverA_i
host 10.0.0.100
object network serverB_o
host 192.168.5.101
object network serverB_i
host 10.0.0.101
object network 192-168-1-NAT-POOL
range 192.168.1.50 192.168.1.239
nat (inside,outside-1) source static serverA_i serverA_o
nat (inside,outside-5) source static serverB_i serverB_o
nat (inside,outside-1) source dynamic any 192-168-1-NAT-POOL interface
object network serverA_i
nat (inside,outside-1) static serverA_o
object network serverB_i
nat (inside,outside-5) static serverB_o
route outside-1 0.0.0.0 0.0.0.0 192.168.1.1 1
route outside-5 0.0.0.0 0.0.0.0 192.168.5.1 2
When I set this up my serverB shows a Public IP of something in the 192-168-1-NAT-POOL Not 192.168.5.101
Any Suggestions?
Thanks!

Not sure why I have Multiple Entries. )-: I did think it was Odd. I think it might be because I looking at examples of the new and old styles of NAT.
We have a Single ISP, though have 2 separate non-Contiguous Class C Addresses from them. We host some Servers on one subnet and some on the other.
I'm looking for a way to use both Subnets on the same ASA.
The Connection to the net looks like this:
Internet -> Edge Router Layer3 VLAN Switch
GE0/1.2 - 192.168.1.1 VLAN Tagged --> GE0 - VLAN Tagged
GE0/1.2 - 192.168.5.1 VLAN Tagged -^
Layer3 VLAN Switch Firewall
GE1 192.168.1.0/24 Untagged -> ASA Outside-1
GE2 192.168.5.0/24 Untagged -> ASA Outside-5
Firewall
ASA inside 10.0.0.0/16 -> Switch -> 10.0.0.100
Hope that helps clarify.
I could try to post some sanitized Configs of my PIX and ASA if needed. But the end result I'm trying to do is have the ASA do NAT for multiple Public Subnets.

Cisco CP (ccp) on different subnets

Hello!
We currently have lots of branches around the world (at about 20) using a class A subnet segmented in many different subnets.
The point is that we would like to use Cisco CP (professional) to perform some monitoring on our routers, but once they are in different subnets and ccp technical datasheet says that it'd work only within the same subnet (client/PC and router).
I'd like to know if someone know how to make CCP works accessing different subnet router's.
If it's not possible, you guys now another tool that may help us to provide some monitoring options of remote routers similar to CCP?
We are currently using CLI for everything and sometimes we need to kind of meshup everything to have a graphic, etc.
Thanks in advance.
Daniel

Thanks.
I managed to make it works and now its running well... i can open CCP and see some graphics.
But i'm trying to view TOP TALKERS and TOP PROTOCOLS using netflow and even after prepairing netflow as requested by CCP it stills getting no answer... no data.
All grapchis and info that i can reach by SNMP (fan speed, cpu, cache, memory, etc) is showing up, but all that i need to get by netflow is empty.
I'm testing on following router:
Cisco IOS Software, C2951 Software (C2951-UNIVERSALK9-M), Version 15.1(3)T4, RELEASE SOFTWARE (fc1)

PROBLEM IN SUBNETs CLASSFULL AND CLASSLESS!!!!!!!

SUBNET PROBLEM
In classfull we can use 10.0.0.0/8 as class A so we can start subnettting from /8/9...upto/32 so in short we have to start from /8 ..upto /8 all r NETWORK....
But in classless 10.0.0.0 we can use from /1 right or /25 or any mask
Questions::
1-why no need to start from /8 on class A
/16 on class B etc ...why ??
2-why we can use NETWORK bits upto /9 /10/15 etc ....????
3-how to know I have been ask on 10.0.0.0/8 from classA(classfull) or classless so how to calculate???
I have good picture example attached with this message...
In that I used 172.16.1.1/16 so in classfull 172.16.0.0/16 start host from /17 right??? so UPTO /16 ALL ARE NETWORK AFTER THAT SUBNET AND HOSTlike in my picture
but in classless picture calculator start from /20 as well and UPTO /20 ALL ARE NETWORK AND AFTER THAT HOST AND SUBNET??why???

Hi Anand,
IPv4 Ip address is 32 bit Binary address and which contains four octets.
so each octet is represented by eight bits
8 bit
7 Bit
6 Bit
5 Bit
4 Bit
3 Bit
2 Bit
1 Bit
128
64
32
16
8
4
2
1
Class A
0-127
0
1
1
1
1
1
1
1
Class B
128-191
1
0
1
1
1
1
1
1
Class C
192-224
1
1
0
1
1
1
1
1
In Classfull,Class A network i.e 8 bit value 128 will never become one.In any other bit it may be 0 or one.at most it can have a value of 127.thats how classfull network defined.
Class A Network 10.0.0.0 can be represented has
10= (128*0)+(64*0)+(32*0)+(16*0)+(8*1)+(4*0)+(2*1)+(1*0)
   =8+2=10
0=(128*0)+(64*0)+(32*0)+(16*0)+(8*0)+(4*0)+(2*0)+(1*0)
=0
0=(128*0)+(64*0)+(32*0)+(16*0)+(8*0)+(4*0)+(2*0)+(1*0)
=0
0=(128*0)+(64*0)+(32*0)+(16*0)+(8*0)+(4*0)+(2*0)+(1*0)
=0
For class A Subnet mask
255= (128*1)+(64*1)+(32*1)+(16*1)+(8*1)+(4*1)+(2*1)+(1*1)
   =128+64+32+16+8+4+2+1
   =255
0=(128*0)+(64*0)+(32*0)+(16*0)+(8*0)+(4*0)+(2*0)+(1*0)
=0
0=(128*0)+(64*0)+(32*0)+(16*0)+(8*0)+(4*0)+(2*0)+(1*0)
=0
0=(128*0)+(64*0)+(32*0)+(16*0)+(8*0)+(4*0)+(2*0)+(1*0)
=0
For class A-It will start from 0-126,subnet will be 255.0.0.0 i.e /8
For Class B it will start from 128-192,subnet will 255.255.0.0.i.e /16
For Class C,it will start from 192-224,subnet will be 255.255.255.0 i.e /24
These are classfull networks.
In Classless network,as per our requirement changes will be done to subnet mask
In your Classfulll screen diagram,you have assigined 20 bits for network and 12 bit for host and for 16 subnets.i.e /20 network
In your classless,you have assigned 24 bit for network and 8 bit for host i.e /24 network
Regards,
Guru

LRT224 Support for multiple subnets

I am considering purchasing an LRT224, but need help with one thing.
The network I manage has about 200 devices currently, with mixed brands and types of switches, access points, etc, scattered about. It is a small school that has had many different people running IT at it, some not so good, others better. Now I manage it.
We would like to add more devices, but currently we are limited to 254 devices. In the LRT224 manual, it -looks- like you can manually specify the subnet mask, and DHCP server range. For example, could I change the subnet mask to 255.255.252.0, or a /22 subnet, and then specify the DHCP range to be, for example only, 192.168.1.2 through 192.168.4.254, for 1024 total addresses? I want to do this without using VLANs, because I'm unsure if any of out switches support VLAN tagging, and I have zero experience with VLANs.
Please let me know, thanks!
Solved!
Go to Solution.

For site-to-site IPsec VPN tunnels, LRT224 supports subnet masks larger than 255.255.255.0. However the local subnets on the LAN side of LRT224 are limited to a class C subnet per VLAN.

WRT300N: Class C routing & NAT

Hi,
I've just been brought in to as a network admin to manage the network of small 'net cafe. The network the admin before had setup really turned out to be a disaster.
Okay, here's the breakdown of the equipment I have available:
30 hosts
3 switches (10 hosts each)
1 WRT300N broadband router
Note: Wireless services are not being used
The ISP over here has assigned us five IP addresses, but since we have 30 hosts we obviously need to use NAT.
What I would like to do is implement some sort of Class C subnetting for the three groups of hosts connected into the switches.
I'd like to use subnets of either 192.168.1.0-192.168.3.0 (255.255.255.0) or even a mask of 255.255.255.240 since a block size of 16 on each subnet will be sufficient. (Each switch is connected into a port of the WRT300N).
My questions are: Can I accomplish this using just the WRT300N and still be able to use NAT to enable my hosts to access the 'net through ADSL? And if so, how? And if this is not possible, then do I need to get another Linksys router so that I can get my network up and running smoothly by connecting the WRT300N to the new router and then connecting the switches to the new router as well? If this is the case, which wireless router would all of you recommend I get?
The name of the game here is to optimize speed, so I'd really like to break down the broadcast domains by subnetting.
Thanks in advance.
- T.

Yes you can use the router WRT350N for using the NAT settings on the router ....
You can connect the router in between Modem & Switch ...

802.1x with /21 subnet

Hello,
I am currently deploying 802.1x using following devices:
XP - HP Procurve - Cisco ACS - Active Directory
I am able to forward dynamic vlan id to employe and consultant after authentication.
Bit how to deal with big site having a large number of people?
Without 802.1x, they are splitted in class C subnet to restrict obvious big subnet limitation like broadcast domain.
How to assign a pool of vlans to one group of users instead of 1 vlan?
Thanks for your help.Stephane

802.1X authenticated ports are assigned to a VLAN that is based on the username of the host that is connected to the port. VLAN assignments work with the RADIUS server, which has a database of username-to-VLAN mappings. After a successful 802.1X authentication of the port, the RADIUS server sends the VLAN in which the user needs to be given access.
Refer to http://www.cisco.com/en/US/products/hw/switches/ps4324/products_configuration_guide_chapter09186a00801eca01.html#wp998917

Subnet Route masks

Hello,
We've run out of IP address on one of our class C networks, so what I trying to do is change the subnet mask of the Class C from 255.255.255.0 to 255.255.252.0, thus giving us 1056 route-able address.
This seems to work well everywhere except in the routing table of our DNS server which happens to be A NW65 SP8 box with Border 3.9.
For example I added added extra NICs to the servers on this subnet running out of IPs and set up workstations with IPs in the 192.168.200.0/22 range and we can log into the servers, I added routes to our layer 3 switches and we can route to our SuperLumin's box (not in production yet) and we can access the internet. But when we try to access other devices on our network using DNS or try to access the internet using the Border box (production box) we can not.
When I tried to add the route to the box using inetcfg it seem to add, but using TCPCON the route isn't showing up and when I try to add the route through TCPCON I get an error stating the subnet mask is less than the default.
I haven't finished testing the SuperLumin's box yet, so moving it into production isn't an option at this time. Does anyone have any suggestions on how to get around this limitation in Netware. Or do I just need to bite the bullet and move to a class B subnet.
Allen

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
First, you'd have 1022 usable addresses, not 1056 ((256*4)-2). I
believe I've heard in the past that NetWare's TCP/IP stack, while
typically handling this well, does not support the situation where it is
doing routing of "odd" netmasks such as /22. If you put your NetWare
box somewhere that it doesn't need to see this network excitement (for
example, on its own class C) and let the router handle all of this type
of traffic (perhaps putting NW in a DMZ or something) then this should
go away. I also sort of thought this was specific to when NetWare was
acting as a router but perhaps it's whenever NetWare is needing to do
any calculations for routing at all in this area.
Going to a Class B would also help if you've identified the issue
correctly, but it may be easier to just have the network's routers do
the routing and put the NetWare box where it is free from this type of work.
Good luck.
Want to yell at me in person?
Come to BrainShare 2011 in October: http://tinyurl.com/brainshare2011
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.15 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
iQIcBAEBAgAGBQJOj3E/AAoJEF+XTK08PnB5RwQP/2ndwkEY7XQvH97yfF1QzgWD
EDy/XdmEGttMKIsXG18iJQbnJFrrFWoZ3CjVvt9J6iuzgv18/HAsJu2riLJGMKVa
m+lWB8u8+l+E+VEhB+2U9fxpqq3uHprTWHODPYtOa8/1eZYA1UpHbWkYuZhWr3ua
Nl8UmuMrOIDCKRoGR+a2IOr+H1PLorUfeSZVv6K+5ggTnA6wGe NFfnx95pSy0tzs
ExOacaUeaXbSceaaOCHOg5ePybP7MWodX+MJNAc7QXgzAIHmi5 yLVBvSH27Qs6kY
y/HYBe/eWleJ1nm6JahlNVi5HKGS1CRzoPmY3/XkiY7jWSvpNF3KhJr5qpcu/QlC
4gT/2xb9uMjLL3o5yO2Qi5O8VK/fN7XZ87Jl9hDbBHcJTRsHjyrXGy7V1aqgzsDp
ojlx43lwcWnu8r9ZdKTBerevRu/nib7bRsl5aZYbUTRIssmHzwRD1RHksfK+6SPv
cic61n3vVTElY4btATrHnsVczOye1fHmag8nDFfq0SpsFMZ773 e/jDut1+lsPXv6
8AxfaO+deTvlf3l2P/rDTYZefB/mm7kgwjZcyXPcoHyyv6KvNcXlZELTMtaVW+5J
twEINdQAepEGHHviS6LKrhowjSy3XaoDW6S2fW59CIL246Y21b xBia85j5AHa0VK
Qhordxjrk2EHF9P6dLCr
=TmLY
-----END PGP SIGNATURE-----

Dhcp and different subnet design

We are trying to determine what is the best design for subnetting. We are moving into a building that has 4 floors. We are considering whether we should create class C subnet for each of the floors or just rather create a supernet of 4 continuous class C subnets. We are also using dhcp to assing IP to the user computers.
I am wondering if a user with his laptop disconnects from the network without releasing the IP and not turning the computer off and then goes to another floor and connects to the network, if the computer will automatically pick up a new IP in the appropriate subnet? We have windows 2000 and XP OS. I have heard some saying that it is automatic and others saying that you have to release and renew. I would appreciate if I can get a straight story from someone here. Thanks for the help.

How many switches are you looking at and how will they be connected? I think this will determine what the VLAN/IP Design will be.
Generally each logical access switch should have a unique user VLAN (and a Voice VLAN if you are deploying voice as well?). So for example if you have a 2950 with 48 ports then you should have an IP network with a /26 subnet mask (max 62-hosts). If you have a stack of two 3750's with 48-ports in each you should have a /25 subnet (max 128-hosts).
The issue you mention about DHCP should not be a problem; if the User moves his PC into a different network the DHCP request should be NAC'd by the DHCP server and he should be offered a new IP address in the correct subnet. Windows 2000 & XP detect the network connection so if you disconnect the cable it shuts the interface down. When you re-attach the cable Windows will attempt to keep the DHCP-assigned address by contacting the DHCP server, if you are on a different network the DHCP server will NAC the request and offer a new IP address. This used to be a problem with NT 4 and WIndows 95 as they didn't detect the network connection.
HTH
Andy

HTTP Proxy - Allowed Subnet

I'm trying to create a rule that will allow web traffic to a class B
subnet.
First rule:
I have Action - Allow, Source - Any, Access - HTTP Proxy, Desitanation -
Specified IP list; The Destination List correctly lists the subnet (e.g.
192.168.0.0/255.255.0.0). I currently have origin server port 80 to 9998
for testing.
Second rule:
I allow some specific URLs. Action - Allow, Source - Any, Access - URL,
Destination - Secified URL list.
Third rule:
Dropping all other web traffic for a test user. Action - Deny, Source -
user.ou, Access HTTP proxy, Destination - Any
Last rule:
Allow all other web traffic. Action - Allow, Source - ou, Access - HTTP
Proxy
Behavior - Logging on as test user (user.ou). User can browse specified
URLs in second rule, cannot browse sites with IPs in subnet specified in
first rule. Only websites allowed seem to be sites specified in URL list in
rule 2.
I'm using craig's proxy.cfg... Seems like this used to work in the past. Am
I missing a setting or completely missing the boat on how these rules are
supposed to work.

Larry P wrote:
> mysterious <[email protected]> wrote in news:bi3ch.5958$jS4.5244@prv-
> forum2.provo.novell.com:
>
>> Larry P wrote:
>>
>>
>>> It seems as though it is only checking by URLs and that none of the IP
>>> based rules are functioning properly.
>>
>> In addion to Cat request, can you post your proxy.cfg as well?
>>
>> Thanks
>>
>> Gonzalo
>>
>>
>
> You got me on the right track...
>
> From my proxy.cfg:
> ; From the BM38FP3C/BM37FP4D patch, fixes 403 forbidden errors
> ; randomly generated after installing bm37sp3
> DonotSendIPToACL =1
>
> Remarking it out fixed the problem.
>
> Thanks Cat and Gonzalo
not really. This was my suspicion and i've checked and when this setting
is set to 1, destination subnets are not being computed by aclcheck.
When set to 0 or rem it out, it will do but then you can run into issues
with multihoming servers and get 403 forbidden on sites that they should
be allowed.
The issue with the switch is only computing destination subnets but not
with ip address so my advice would be to set the switch to 1 and change
your rule to "type" "URL" and then enter as destiantion
http://xx.xx.xx.xx, the ip address of one of the host. Then on the same
rule, enter again http://yy.yy.yy.yy for the second host and
successively all other hosts on the subnet. This will work and even is a
little more work to enter one by one, it will be better than turn the
switch on the proxy.cfg out
Gonzalo

WRT300N - we need to use Subnet 255.255.252.0 for our network

We bought a WRT350N and two WRT300N's recently and are excited about the speed increase over 802.11g as well as the range improvements. However, in configuring them we have found we can't put in our subnet 255.255.252.0. Is there a way to add a subnet to the dropdown? If not, are we going to have to return these and go with a different brand's Wireless-N? We are not wanting to setup our few Wireless devices on DHCP through the WRT3xxN's. Are these routers just not supposed to be used on a W2K Domain?
Message Edited by DES1 on 10-04-2007 08:54 AM

Hi...this is a router limitation....works on "class C" subnets only

Class A Subnet

Similar Messages

Maybe you are looking for