Member Avatar for computernuts

I have a ADSL router with a static ip connected to a switch which is serving 48 PC's. The pc are configured to use DHCP from the router.. Some times some of the pc's show limited or no connectivity. I earlier thought that it might be a problem with the lan catd or the switch but when i gave static IP's to the lan cards it was able to comunnicate with the network properly.. but if i do that i cannot access the Internet. I think it has some thing to do with the router. We use utstar ADSL Router provide by the service provider.

Pls advice

  • 2 Contributors
  • 2 Replies
  • 183 Views
  • 2 Days Discussion Span
  • Latest Post Latest Post by computernuts

Dani AI

Generated

Problem recap: described an ADSL gateway on a switch serving ~48 PCs by DHCP. Some workstations intermittently report “limited/no connectivity”; assigning static IPs lets them talk on the LAN but removes Internet access. rightly flagged DHCP/resource limits as suspects. The steps below focus on isolating whether the failure is DHCP, switch/port layer, NAT/firewall limits, or an ISP/PPPoE issue — and on safe, low-risk fixes.

Quick diagnostic checklist (capture these when the fault appears):

ipconfig /all
ping <router_LAN_IP>
ping 8.8.8.8
nslookup example.com
arp -a

Interpretation notes: an address in 169.254.x.x = no DHCP lease. If a machine has a valid LAN IP but cannot ping the router, suspect switch/cabling/duplex. If it pings the router but not 8.8.8.8, suspect NAT/ISP. If 8.8.8.8 pings succeed but DNS names fail, DNS is the issue.

Practical fixes and checks:

  • Inspect the router’s DHCP table: count active leases vs scope size and note lease duration. If the scope is too small or lease time very short, increase the scope and lengthen leases to reduce churn.
  • Watch NAT/session usage on the router; many consumer ADSL boxes run out of translation entries under moderate load. If translations spike, either move to a device with a larger NAT table or offload clients behind a dedicated router.
  • Verify there are no duplicate DHCP servers on the LAN and that static IPs don’t collide with the DHCP pool.
  • On the switch: check port errors, link speed/duplex mismatches, and flapping ports; replace suspect patch cables and update NIC drivers on problem machines.
  • Use DHCP reservations for servers/printers and keep critical devices static outside the DHCP range.

Guidance before replacing hardware: reproduce the failure with controlled tests (continuous pings to the router and to a public IP while cycling leases) and ask the ISP whether they limit concurrent sessions or require PPPoE on the provider device. If replacement is needed, choose a business-class gateway that publishes DHCP pool limits, NAT/session capacity, syslog support and firmware updates — or run DHCP on a dedicated server or small appliance for reliability.

Recommended Answers

All 2 Replies

Member Avatar for Monte

Limited or no connectivity usually occurs when your DHCP server is down on a network. It could be your Internet service provider's server, your personal router, or your DHCP provider. Check to see if you have an IP address when it's in limited mode. It works when you give it a static ip because there is no DHCP server and no ip gets renewed. My guess is your router can't handle all those connections and bandwidth.

If i was you, with 48 connections... i'd go ahead buy a decent router and set one of those pc's as a server using windows 2003 and that way your other computers will connect to that computer to get their IP info and it won't keep dropping. There are many advantages of windows server 2003.

Or if you really wanted to, you could set all 48 computers their own static ip. the gatway address would be your router ip and the dns ip would also be the routers ip. (This would only help if the problem was due to dhcp errors on the router. If its because the router is overloaded it will still drop connection)

Member Avatar for computernuts

Can u suggest me some good router... I was thinking to go in for dlink 502T router

Thanks and regards

Limited or no connectivity usually occurs when your DHCP server is down on a network. It could be your Internet service provider's server, your personal router, or your DHCP provider. Check to see if you have an IP address when it's in limited mode. It works when you give it a static ip because there is no DHCP server and no ip gets renewed. My guess is your router can't handle all those connections and bandwidth.

If i was you, with 48 connections... i'd go ahead buy a decent router and set one of those pc's as a server using windows 2003 and that way your other computers will connect to that computer to get their IP info and it won't keep dropping. There are many advantages of windows server 2003.

Or if you really wanted to, you could set all 48 computers their own static ip. the gatway address would be your router ip and the dns ip would also be the routers ip. (This would only help if the problem was due to dhcp errors on the router. If its because the router is overloaded it will still drop connection)

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.