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  • Obtaining a DHCP IP address if static address is not available

    - by user142485
    I have seen some questions that are similar to my problem but not a good solution. Ex. User has a laptop and has a static IP address at the office. They also take the laptop off site where they also need internet. Is there a way to configure their computer so that it will obtain an IP address automatically when the configured static address is not available (without making the user go into network configuration and changing to obtain automatically)?

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  • ISC DHCPD IPv6 for multiple interfaces

    - by Seoman
    I want to assign multiple IPv6 to a server with multiple NIC. As IPv6 RFC defines, each server has a unique DUID that can have one of the 3 formats (LL, LLT or enterprise). And each NIC has an IAID. So a request from NIC1 its the DUID and the IAID of the NIC1 and the request from NIC2 its the same DUID but the IAID its different. The problem is that from a Centos box, when I ask for an IP in 2 different interfaces, I get the same IP. I can't find how to specify host entry based on DUID and the IAID. I see some people generating a unique DUID based on the MAC of the NIC but this is not IPv6 RFC says. What I tried is: host entry1 { host-identifier option dhcp6.client-id 00:01:00:01:19:fc:f8:1c:52:54:00:7e:c9:ec; option dhcp6.ia-na "00:09:40:5d"; fixed-address6 2001:db8:0:1::202; } host entry2 { host-identifier option dhcp6.client-id 00:01:00:01:19:fc:f8:1c:52:54:00:7e:c9:ec; option dhcp6.ia-na "00:7e:c9:ec"; fixed-address6 2001:db8:0:1::201; } This causes a Segmentation Fault in the client (what is scary...). I guess is not the right use for ia-na option but I don't see any other option.

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  • Discovering the default gateway without DHCP

    - by JavaRocky
    A crazy question, but is there anyway to discover the default gateway without DHCP? This would be for a device on a network which does not use DHCP which does not have an IP address as yet. I was thinking if I could discover the default gateway, then i could try to guess an unused ip address then broadcast on the network to see if it's being used. I may be asking for trouble i understand. E.g. if there is already a computer which has a static IP and is shutdown.

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  • Is DHCP required on a Win2003 secondary DNS server?

    - by Mark
    We have a secondary DNS server and we've been noticing that the DNS.exe process is getting rather large. (Like, rebooting the server large) I read something somewhere that 2k3 has two relevant memory leak issues, one is the DNS (supposedly fixed in 2007), and another for DHCP. DHCP is running on this server, but I don't see why. Hence my question. Is the DHCP service required for (secondary) DNS to function? Server has: 24 cores (X5650), 8GB RAM

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  • ISC DHCP - Force clients to get a new IP address, instead of the being re-issued their previous lease's IP

    - by kce
    We are in the middle of a migration of our DHCP and DNS services from a Debian-based server to a Windows Server 2008 R2 implementation. The Debian server is running isc-dhcpd-V3.1.1. All of workstations are configured to have fixed-addresses between .3 and .40 (the motivation behind that choice is mostly management/political much like here). DHCP leases are given out in the range of .100 to .175. Statically configured servers live in the .200 block and above (which is mostly empty). When we move to the Windows platform, management/political considerations require me to move the IP ranges around again. We would like to keep .1 - .10 reserved for network appliances, switches, and other infrastructure. .200 will remain designated for servers. The addressing space in between should be available to clients and IPs should be dynamically allocated (Edit: instead of automatic as originally mentioned) by the server. My Address Pool on the Windows Server looks like this: 192.168.0.1 192.168.0.254 (Address range for distribution) 192.168.0.1 192.168.0.10 (IP addresses excluded from distribution) 192.168.0.200 192.168.0.254 (IP addresses excluded from distribution) Currently, we have all of our clients still on the .3 - .40 range, and a few machines still active in the .100 - .175 (although there are lots devices that are powered off that still have expired leases with IPs from that range). Since the lease "database" isn't shared between the old and new DHCP server how can I prevent clients from receiving a lease with an IP address that is currently being held by client with a non-expired lease from the old DHCP server? If I just expand the range on the Debian DHCP server to be 192.168.0.10 - 192.168.0.199 is there a way to force clients to not re-use their old IP address when they send their DHCPDISCOVER? Can I make the Windows DHCP server be authoritiative like the ISC implementation? The dhcpd.conf from the Debian server: ddns-update-style none; authoritative; default-lease-time 43200; #12 hours max-lease-time 86400; #24 hours subnet 192.168.0.0 netmask 255.255.255.0 { option routers 192.168.0.1; option subnet-mask 255.255.255.0; option broadcast-address 192.168.0.255; range 192.168.0.100 192.168.0.175; } host workstation-1 { hardware ethernet 00:11:22:33:44:55; fixed-address 192.168.0.3; } ... and so on until 192.168.0.40

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  • How to force Windows 7 to ask for a "fresh" IP address from DHCP server?

    - by haimg
    I'm troubleshooting a certain issue with my DHCP configuration, and need my Windows machine to ask for a "fresh" IP address, so I can see which address DHCP server gives by default. When I do ipconfig /release followed by ipconfig /renew, Windows "proposes" its old IP address to the DHCP server (just checked with Wireshark, initial "DHCP Discover" message has Option-50 (requested IP address) with Windows machine's old IP). Tried disabling/enabling network adapter. Same behavior. Question: How can I force Windows to just ask for a new IP address, without proposing its old IP address.

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  • How to configure Windows Server 2008 DHCP to supply unique subnet to a remote site?

    - by caleban
    The Main site hosts the only Windows Server. Windows Server 2008 R2 Domain Controller running AD, DNS, DHCP, Exchange 2007. Remote site has no Windows server. Main site subnet is 192.168.1.0/24 Remote site subnet is 192.168.2.0/24 The Windows Server at Main site is supplying 192.168.1.0/24 via DHCP to hosts at the local site where it resides. Is it possible to configure that Windows Server to supply 192.168.2.0/24 to hosts at the Remote site and if so how? We could use the Cisco router at the Remote site to supply DHCP but if possible we'd like to use the Windows Server at the Main site to supply DHCP.

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  • How to setup dhcp3-server to advertise the DNS server the server itself has got from DHCP?

    - by Ivan
    The Ubuntu 10.04 server has eth0 Internet interface configured by means of an ISP's DHCP. At the same time the server has static eth0 LAN interface to which it provides masquerading (NAT) and LAN-internal DHCP service (dhcp3-server). As far as I've understood the manual, I had to hardcode DNS servers to advertise through LAN DHCP with option domain-name-servers in dhcpd.conf. But what if the ISP changes his DNS server IP silently (we use a SOHO-class ISP, so this won't surprise me much)? Can I configure dhcpd to advertise the DNS server the server uses itself, the one gotten by its DHCP client mechanism?

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  • dhclient.conf: Send 2x host-names to the DHCP server?

    - by RobM
    Already working: Debian box DHCP with send host-name me.company.com in dhclient.conf DNS updates automatically with an entry for me.company.com What I want to add: Send a second host-name, so both are automatically registered with DNS In other words: I want a DHCP client to register with DNS twice using different names, preferably without having to maintain DNS records manually. Is this even possible with DHCP?

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  • Can't ping devices by IP address for devices allocated IPs by DHCP

    - by GiddyUpHorsey
    I have a home network with a Trendnet wireless router and a Windows Domain. The Domain Controller/DNS server is a Windows 2000 Server and is configured to forward queries to DNS servers provided by the ISP. The router provides DHCP and is configured with the Windows 2000 Server as the DNS server. The network has been set up for a couple of years and usually works fine. When I connect iPhones to the network over WiFi, the router can ping the iPhones through its browser based admin interface, but Windows machines that are part of the Windows Domain cannot. A laptop was connected to the network over WiFi that wasn't joined to the domain and it could see the iPhones. The router UI shows that the laptop has a reserved IP allocated via DHCP. All machines either have a static or DHCP allocated IP on the 192.168.0.* subnet. Router - 192.168.0.1 - Static - Wired Windows Domain Controller - 192.168.0.8 - Static - Virtual Windows 7 Workstation - 192.168.0.200 - DHCP Auto - Wired VMWare ESXi Host - 192.168.0.201 - Static? - Wired iPhone 1 - 192.168.0.202 - DHCP Auto - WiFi iPhone 2 - 192.168.0.203 - DHCP Auto - WiFi Windows Vista Laptop - 192.168.0.204 - DHCP Reserved - WiFi Using the Windows 7 machine (200), I try to ping each machine and the only DHCP machine that responds is itself. The other DHCP machines fail with Reply from 192.168.0.200: Destination host unreachable.. Using nslookup fails with *** domain.controller.name can't find 192.168.0.203: Non-existent domain. Using the Windows 2000 Domain Controller (8), I try to ping each machine and the only DHCP machine that responds is the Windows 7 machine (200). Pinging the other DHCP machines fails with Request timed out.. Using nslookup also fails with *** domain.controller.name can't find 192.168.0.203: Non-existent domain. Using the iPhone 2 (203), I try to ping (Network Ping Lite) the machines with static IP addresses and that works fine. When I try to ping the Windows 7 machine (200) it is unable to get a response. How do I configure the DNS server/Windows Domain/Router properly so that the Windows Domain machines can see the IPs allocated via DHCP?

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  • How do I protect a low budget network from rogue DHCP servers?

    - by Kenned
    I am helping a friend manage a shared internet connection in an apartment buildling with 80 apartments - 8 stairways with 10 apartments in each. The network is laid out with the internet router at one end of the building, connected to a cheap non-managed 16 port switch in the first stairway where the first 10 apartments are also connected. One port is connected to another 16 port cheapo switch in the next stairway, where those 10 apartments are connected, and so forth. Sort of a daisy chain of switches, with 10 apartments as spokes on each "daisy". The building is a U-shape, approximately 50 x 50 meters, 20 meters high - so from the router to the farthest apartment it’s probably around 200 meters including up-and-down stairways. We have a fair bit of problems with people hooking up wifi-routers the wrong way, creating rogue DHCP servers which interrupt large groups of the users and we wish to solve this problem by making the network smarter (instead of doing a physical unplugging binary search). With my limited networking skills, I see two ways - DHCP-snooping or splitting the entire network into separate VLANS for each apartment. Separate VLANS gives each apartment their own private connection to the router, while DHCP snooping will still allow LAN gaming and file sharing. Will DHCP snooping work with this kind of network topology, or does that rely on the network being in a proper hub-and-spoke-configuration? I am not sure if there are different levels of DHCP snooping - say like expensive Cisco switches will do anything, but inexpensive ones like TP-Link, D-Link or Netgear will only do it in certain topologies? And will basic VLAN support be good enough for this topology? I guess even cheap managed switches can tag traffic from each port with it’s own VLAN tag, but when the next switch in the daisy chain receives the packet on it’s “downlink” port, wouldn’t it strip or replace the VLAN tag with it’s own trunk-tag (or whatever the name is for the backbone traffic). Money is tight, and I don’t think we can afford professional grade Cisco (I have been campaigning for this for years), so I’d love some advice on which solution has the best support on low-end network equipment and if there are some specific models that are recommended? For instance low-end HP switches or even budget brands like TP-Link, D-Link etc. If I have overlooked another way to solve this problem it is due to my lack of knowledge. :)

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  • How can I determine the IP addresses allocated by DHCP on a router that I'm connected to?

    - by user234831
    This "router" is not a typical situation. I'm using my phone as a hotspot and can only configure a select number of DHCP options. I can manage the limit on how many devices/clients can use my phone as a hotspot. I have to select from a radio-button list with the options: 2,3,4,5, or 8 I can specify the DHCP starting IP address. In this case, it begins at 192.168.6.106 When I'm connected via WIFI to my phone, an ipconfig /all command shows me that the default gateway is 192.168.6.1 and my IPv4 address is 192.168.1.148. I have the luxury of connecting another device to the phone and that device was assigned 192.168.1.121. I've tried connecting to 192.168.6.1, hoping for some sort of router setup page that I'm used to seeing, but there is no such thing or maybe it's just a matter of incompatable operating systems. In summary, the "router" (phone) has an IP address of 192.168.6.1 and a DHCP server that begins at 192.168.6.106 and allows up to 8 connections. Normally, I would assume a range of 192.168.6.106 - 192.168.6.113, but connected clients are showing otherwise. How can I figure out which IP addresses are set aside by DHCP for clients?

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  • How to statically configure DNS servers on a Cisco router when the WAN interface uses DHCP?

    - by Massimo
    I have a Cisco router (model 887VA, IOS 15.4) used to connect a LAN to the Internet via ADSL. The WAN interface uses DHCP: interface ATM0.1 point-to-point ip address dhcp I need the router to use a statically-defined DNS server for name resolution: ip name-server A.B.C.D However, the router insists on using the DNS servers supplied by the ISP via DHCP: Router#ping www.google.com Translating "www.google.com"...domain server (<ISP DNS>) [OK] Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 173.194.116.208, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 44/45/48 ms How can I tell the router to ignore the ISP-supplied DNS servers and only use the statically-configured one?

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  • How to make a DHCP server on virtual machine serves other virtual machines(on different physical machines)?

    - by Tony
    I'm building a virtual cluster with VirtualBox and Opensuse. I have 10 physical machines and need several vms on each. The virtual machines are supposed to be in a "private" network, but still have internet access. I was asked to set up a virtual head node working as DHCP server. I installed DHCP server on the virtual head node and it seems works. On VirtualBox I set 2 network adapters to the head node, one bridged adapter and one internal network. One vm on the same physical machine has been set nic as internal network adapter. The vm can get IP address (so DHCP works) but can't access internet. What should I do? Specifically, what network adapter should I choose for head-node and work-nodes in VirtualBox? What in the virtual machines should I do?

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  • Why do partially failed/failing switches fail to pass DHCP?

    - by David Mackintosh
    I've noticed this several times: a switch starts to behave oddly. Usually if the switch doesn't fail outright, what tends to get noticed is that DHCP doesn't work. We had a Linksys SRW-224P fail today. Systems which were still connected worked properly, until it came time to renew their DHCP lease. Once the lease expired, they stopped working, but up until then we couldn't detect a failure. This includes PoE VoIP phones -- they work fine until their lease is up, at which point they're done. I've noticed this on the above-mentioned Linksys, three varieties of 3Com, and possibly half a dozen dumb switches. What is it about DHCP that makes it sensitive to failing switches?

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  • Transferring DHCP using Windows Server Migration Tool - Why is Powershell is crashing on the import of the .mig file?

    - by Mike
    I am migrating DHCP from a windows server 2003R2 DC to a Windows Server 2008R2 DC I've followed this video and its predecessor (Installing Windows Server Migration Tools) http://technet.microsoft.com/en-us/video/migrating-dhcp-using-the-windows-server-2008-r2-migration-tools.aspx I went through everything smoothly until the last step. I have exported a .mig file with my DHCP configuration on the old 2003r2 server. I transferred this .mig file over to my 2008R2 server, when running the import command, it will appear to work for a minute or two and then I get a generic windows "Powershell has stopped working" error and I have to close the program. Under the problem details I see the following: FileVersionOfSystemManagementAutomation: 6.1.7600.16385 InnermostExceptionType: System.AccessViolationException OutermostExceptionType: System.AccessViolationException DeepestPowerShellFrame: unknown OS Version: 6.1.7600.2.0.0.272.7 LocaleID: 1033 Seems like there are permissions issues maybe? I am running powershell as an admin and am logged in to the server as a domain administrator. Any Ideas? Thanks

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  • Systemd-networkd: How can I prepend a static nameserver entry to DHCP-discovered nameservers?

    - by runiq
    I'm using systemd 213 on Arch Linux, and systemd-networkd with DHCP to connect to the internet. I'm also running a caching DNS server on 127.0.0.1. I'd like to make this server the first DNS server in the list, but I'd also like to use the nameservers discovered by systemd-networkd's DHCP facility. Using a static resolv.conf isn't really possible, because I connect to networks with different DNS settings. I know I can set fallback DNS servers in /etc/systemd/resolved.conf, but is there a way with systemd-networkd to prepend my local DNS server to those discovered by DHCP?

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  • Why is Server 2012 assigning "169.254.*.*" series when creating DHCP server?

    - by Seth
    I have a small office, with ATT Motorola modem (192.168.1.254) set as passthrough to Dlink DIR-815 (LAN 192.168.0.1) I am trying to setup DHCP server on Server 2012, and when I create new DHCP server, the title is created as 169.254.. instead of the domain name. (Domain clients can retrieve IP's as defined in the scope) Non-domain clients are not receiving IP's from the server but rather the Motorola... How do I assure DHCP setup is properly creating itself, and how do I make sure domain and non-domain clients get IP's from the server?

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  • How can I ask for a new dhcp lease on windows 7?

    - by Pat
    In windows7 how do I request a new dhcp lease ? What I need in the equivalent of the button "repair" on windows XP. The button "diagnose" seems to do a few things but not request a new dhcp lease if one is already available. Disabling and re-enabling the card does the trick but messes up any program capturing traffic on the interface.

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  • No client internet access when setting up these iptables rules

    - by Siriss
    I have read many other posts but cannot figure this out. eth0 is my external connected to a Comcast modem. The server has internet access with no issues. eth1 is internal and running DHCP for the clients. I have DHCP working just fine, all my clients can get an IP and ping the server but they cannot access the internet. I am using ISC-DHCP-SERVER and have set /etc/default/isc-dhcp-server to INTERFACE="eht1" Here is my dhcpd.conf file located in /etc/dhcp/dhcpd.conf ddns-update-style interim; ignore client-updates; subnet 10.0.10.0 netmask 255.255.255.0 { range 10.0.10.10 10.0.10.200; option routers 10.0.10.2; option subnet-mask 255.255.255.0; option domain-name-servers 208.67.222.222, 208.67.220.220; #OpenDNS # option domain-name "example.com"; default-lease-time 21600; max-lease-time 43200; authoritative; } I have made the *net.ipv4.ip_forward=1* change in /etc/sysctl.conf here is my interfaces file: auto lo iface lo inet loopback auto eth0 iface eth0 inet dhcp iface eth1 inet static address 10.0.10.2 netmask 255.255.255.0 network 10.0.10.0 auto eth1 And finally- here is my iptables.conf file: # Firewall configuration written by system-config-firewall # Manual customization of this file is not recommended. *nat :PREROUTING ACCEPT [0:0] :OUTPUT ACCEPT [0:0] :POSTROUTING ACCEPT [0:0] -A POSTROUTING -s 10.0.10.0/24 -o eth0 -j MASQUERADE #-A PREROUTING -i eth0 -p tcp --dport 59668 -j DNAT --to-destination 10.0.10.2:59668 COMMIT *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT -A INPUT -p icmp -j ACCEPT -A INPUT -i lo -j ACCEPT -A INPUT -i eth1 -j ACCEPT -A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT -A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT -A INPUT -m state --state NEW -m tcp -p tcp --dport 443 -j ACCEPT -A INPUT -m state --state NEW -m tcp -p tcp --dport 53 -j ACCEPT -A INPUT -m state --state NEW -m udp -p udp --dport 53 -j ACCEPT -A FORWARD -s 10.0.10.0/24 -o eth0 -j ACCEPT -A FORWARD -d 10.0.10.0/24 -m state --state ESTABLISHED,RELATED -i eth0 -j ACCEPT -A FORWARD -p icmp -j ACCEPT -A FORWARD -i lo -j ACCEPT -A FORWARD -i eth1 -j ACCEPT #-A FORWARD -i eth0 -m state --state NEW -m tcp -p tcp -d 10.0.10.2 --dport 59668 -j ACCEPT -A INPUT -j REJECT --reject-with icmp-host-prohibited -A FORWARD -j REJECT --reject-with icmp-host-prohibited COMMIT I am completely stuck. I cannot figure out why the clients cannot access the internet. Am I missing a service? Is a service not running? Any help would be greatly appreciated. I tried to be as thorough as possible but please let me know if I have missed something. Thank you!

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