Member Avatar for Tim_2

I have an address of 10.--.204.0 at my network. Could you help by telling me how one would go about adding more ip's than the 254 I currently have available? I also have a .205 but this is used or just managment and is routed to its own server. It all comes through the same router (for i can only find one) and I guess is split up in the switch. Am I right in thinking that, since I use the first 8 ports in each switch for mgnt clients, that the switch is configured to have 2 Vlans? I really need help getting to grips with this. I have read ans read about subnetting but all my subnets are 255.255.255.0. I assumed that this meant that I have a 24 bit network address and 8 bits for hosts giving me just 254 addresses to use 'in house'. If this is the case, does this mean that when this was set up, someone purchased the 204 and the 205 connections separately?! I am probably making no sense at all but if anyone out there can help me out a little to understand this I will much appreciate it.......

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Three quick facts to establish before changing anything: whether the extra address block is actually routed to the site (ISP‑side routing vs. provider‑internal use), where NAT terminates, and whether the switch is enforcing VLANs or simply using port groups. and pointed toward the provider/NAT question and gave a good pointer to background reading — those are the right concerns. The fastest way to turn guesses into facts is to inspect the edge/router, the core switch VLAN state, and the DHCP configuration so decisions are based on actual routing and DHCP boundaries.

On Cisco gear the following commands reveal how the LAN/WAN are wired and which device is authoritative for routing/DHCP/NAT:

show ip interface brief
show running-config
show vlan brief
show interfaces trunk
show ip route
show ip nat translations
show ip dhcp binding
show cdp neighbors detail

Brief interpretation: the interface and routing commands show which prefixes are present and whether multiple sub‑interfaces or SVIs exist; VLAN and trunk commands show port membership and whether the switch is passing tagged traffic to the router; NAT and DHCP commands show where address translation and lease assignment live. If the environment uses non‑Cisco kit, equivalent diagnostics (router GUI, switch management pages, DHCP console) will give the same answers.

Three practical paths to get more hosts, with tradeoffs: expand the LAN prefix if full control of the edge device exists (requires coordinated DHCP/gateway changes and downtime); ask the ISP to route a larger or an additional block to the site and attach it to a new VLAN with routing or DHCP relay; or place extra hosts behind NAT (fastest, but not suitable for services needing public IPs). For an AD rollout (Server 2008 acting as DC), ensure at least one DC has a static IP, DNS for clients in every VLAN, and DHCP relay/forwarding configured for remote VLANs. Back up current configs and schedule a maintenance window before making changes, and when contacting the ISP ask specifically whether the second subnet is routed to the premises and whether NAT is applied upstream.

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Member Avatar for lolafuertes

All the addresses starting with 10 are free. In fact, this range of addresses is used internally by big (or not so big) corporations to allow internal private networks, and go to the internet through a router having a poblic internet address.

Some ISP use the 10.x.x.x to get fake 'fixed' ip addresses, which probably is your case.

To allow more addresses in a unique subnet, is enough to change the mask. The mask determines how many elements can be hold in a subnet.

In binary format, the mask has ones in the left side and zeros in the right.
If you apply this mask to any ip address, you'll have the LAN identification.

In fact, the 10.xx.204.0 with a mask of 255.255.255.0 can handle 254 addresses, the self address and the multicast (total 256)
if you apply a mask of 255.255.254.0 instead, you are changing the identifier of the lLAN and, if your equipement can handle this in the right way, will distinguish perfectly both nets having distint mask. Whith this a such mask, you'll handle 510 addresses plus self and multicast.

To change the mask in you network, is not so easy because you need to know how is configured you LAN and WAN equipement, and if they can handle it, to change the way they work with the mask(s).

Probably, the best way will be to contact with your provider for support.

Hope this helps

Edited by lolafuertes
Member Avatar for Tim_2

Thank you for taking the time to reply. This is very helpful. Out of interest, how would I go about finding out how the WAN/LAN is configured? Where would you start if you walked into my network? This week I am having a new server 2008 installed and, although I am fairly confident setting up this as a file, print, DC and AD server myself, the network is is being configured to allow users to log onto both servers. I assume that this will involve some sort of switch (Cisco) reconfiguring. What do you suspect they will do and is there anything you feel I need to look out for or ask in terms of managing the network after this? I know that I am fishing for guidance in a wooly fashion but I am just after some tips...... I have been asked to oversee quite a bit at short notice so I am on a steep learning curve! Thanks again.

Member Avatar for zilgroup

hello,

with an ip in that class u can access the most of the number of valid host there is, and that class of ip is mostly used by big coroperations and as a public ip address that can be routed over the internet. pls do confirm if u have it as a public add from ur ISP and also confirm if the NAT configuration is configured on your router.

Warm Regards,
zil

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