IP isn't automatically assigned from DHCP after CentOS8 install

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srinivas_pithani
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IP isn't automatically assigned from DHCP after CentOS8 install

Post by srinivas_pithani » 2020/02/18 15:19:48

I have got Dell R520 PE and I have installed C8 , went fine . We have cisco switch which acts as DHCP and it assigns the IP ( we have MAC > IP binding there ) . Now , previously on C7 , all went fine i.e. when C7 was installed we get the IP which is needed without any problems but for C8 somehow it picks up different IP .
Currently what I have done is assign a static IP but we have few more machines which we plan to move to C8 , I think something has changed here in C8 which isn't allowing . Static changes works fine without any problem .
No changes at our end i.e interms of network/systems end so any inputs on this would be appreciated .

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TrevorH
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Re: IP isn't automatically assigned from DHCP after CentOS8 install

Post by TrevorH » 2020/02/18 15:53:15

for C8 somehow it picks up different IP .
What sort of ip? Did you check the leases file to see what DHCP server provided it?
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BShT
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Re: IP isn't automatically assigned from DHCP after CentOS8 install

Post by BShT » 2020/02/18 16:06:06

IP leases are anchored at MAC addresses

if you change the MAC address you will get a new IP

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jlehtone
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Re: IP isn't automatically assigned from DHCP after CentOS8 install

Post by jlehtone » 2020/02/18 16:47:19

BShT wrote:
2020/02/18 16:06:06
if you change the MAC address you will get a new IP
OP seems to have same hardware, so same MAC.

Does the cisco have log too?

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TrevorH
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Re: IP isn't automatically assigned from DHCP after CentOS8 install

Post by TrevorH » 2020/02/18 16:48:24

We also don't know if it is, for example, a 169.254 address and locally assigned. Not enough info...
CentOS 6 will die in November 2020 - migrate sooner rather than later!
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BShT
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Re: IP isn't automatically assigned from DHCP after CentOS8 install

Post by BShT » 2020/02/18 17:37:33

you can have a static lease or not, if your lease is not static...

some dhcpd always gives the same IP through updates unless the range is occupied (FreeBSD works as is)

some dhcpd gives random IP through updates (Windows works as is)


lightman47
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Re: IP isn't automatically assigned from DHCP after CentOS8 install

Post by lightman47 » 2020/02/18 18:01:10

some dhcpd always gives the same IP through updates unless the range is occupied (FreeBSD works as is)

some dhcpd gives random IP through updates (Windows works as is)
In addition, many dhcp servers provide for 'assigned/reserved' addresses that you map to the MAC address so that your device gets the same/assigned address, regardless how many devices start & request addresses/leases before yours.

I run dhcp at home, but needed a few of my machines to always have the same (pseudo-static) address each time they connect so that they could be found. You usually won't want to STATIC a laptop. for instance, then take it to you local coffee shop wifi - and have to adjust the settings to get it to connect. Reserved addresses on the dhcp server at home "fixes" that; the laptop is then dhcp all the time, but gets the assigned address when home.
Remember - importing/building packages will likely "byte you in the butt" come update time, long after you'd forgotten you did that! Use repos whenever possible.

srinivas_pithani
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Re: IP isn't automatically assigned from DHCP after CentOS8 install

Post by srinivas_pithani » 2020/02/19 11:44:14

TrevorH wrote:
2020/02/18 15:53:15
for C8 somehow it picks up different IP .
What sort of ip? Did you check the leases file to see what DHCP server provided it?
This is private IP ( 192.168.x.x) . It is a switch which provides the IP not sure if any log is available on that cisco device , I will check on this & get back .

srinivas_pithani
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Re: IP isn't automatically assigned from DHCP after CentOS8 install

Post by srinivas_pithani » 2020/02/19 11:44:56

jlehtone wrote:
2020/02/18 16:47:19
BShT wrote:
2020/02/18 16:06:06
if you change the MAC address you will get a new IP
OP seems to have same hardware, so same MAC.

Does the cisco have log too?
Yes , its same MAC but it doesnt give the problem on C7 - how about that ? I mean if I reinstall with C7 , then all good .

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