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Posts Tagged ‘dhcp’

DHCP Server Logs

Feb 18, 2013 1 comment

There have been several instances where I have been trying to troubleshoot DHCP Issues live, or other cases when I needed to know what computer had a specific IP address in the past…. A useful way to find out this information is to use/view the DHCP server logs. The log keeps only the past 7 days of logs, but through backups, you can actually go back to any point in time.

The log it located at C:\Windows\System32\dhcp

The logs are named dhcpsrvlog-mon; dhcpsrvlog-tues, etc… you get the idea. There is also a separate log to DHCPv6 (IPv6) addreseses.

 

dhcplog

Also, along that lines, don’t specifically trust the DHCP Lease active/inactive status as indicated in the DHCP console. Sometimes a reservation is used for a device that is set statically, so DHCP will show inactive, while the address is actually in use. Also it might show active even though the device isn’t properly receiving an IP address.

Enjoy!

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DHCP Best Practices

Here are several DHCP best practices as collected from various resources including Comp/TIA and Microsoft:

  • Always include the entire subnet in the scope (192.168.1.1 – 192.168.1.254, or 172.29.0.1 – 172.29.255.254)
  • Add exclusions for ranges which are using static IP addresses, and for future growth area, such as setting aside 10 addresses for printers so they stay within the same general IP address range
  • For networks where DHCP services are critcal or for larger networks, consider two DHCP servers configured in an 80/20 split (however, Microsoft Server 2012 has a new provision for redundant DHCP servers)
  • Configure active directory credentials to enable DHCP to update the DNS server with IP address information using secure updates.
  • Use “server side conflict detection” only when needed – this is a feature which delays DHCP from handing out an address until it has first issued an ICMP ping message to check if the address might already be in use but not known by DHCP already (ie statically assigned within the lease range without an exclusion or active lease).
  • Typical DHCP lease time is 8 days, however if you have a separate scope for guest or wireless clients, consider a shorter lease time such as 8 hours; conversely, leases for fixed devices (printers, etc) consider 16-24 days.

Technology Policies/Network Printers

Network Assignment

To properly configure network printers initially on a windows network:

  1. Leave printers setup in DHCP
  2. Check DHCP server and use the MAC address information to establish a DHCP reservation. Remember to set the reservation in ‘all’ DHCP servers.
  3. Restart the network printer as necessary
  4. Add printer on server via TCP/IP address
  5. Deploy via Group Policy

Color Network Printers

  • Configure default color setting as “black & white” which will force the end users to choose color only when the want it.
Rationale: From experience, users will not elect to go through the extra steps required to select black & white when printing and e-mail or website, even when color is not necessary. However, these extra color pages can contribute significantly toward the number of annual color pages.
  • Color printing access: depending on the printer/MFP device, along with its drivers, there are several options to restrict color printing.
  1. Use the printer configuration for access control lists within the printer itself, which will then require a “code/password” on each client’s workstation to be setup.
  2. Create two different shared printers on the server, one of which is black & white only (color disabled) and then use windows ACL to determine who has access to which features