That's not the same subnet though, a subnet is made up of a network and a net ask, if you have 2 separate net asks you have 2 separate subnets.I would like to ask for example 192.168.1.0/24 which has new ip's added that are using /30, can existing or new ip's still use /24 on that subnet?
It's not real clear what your saying, but a general rule of thumb is you can not reuse subnet's, in the same Network, there are some exemptions to that, but not for your case.Originally our WISP network was using OSPF but because of adjacency disconnections on wireless interfaces, we had to start using bridged VLAN's for PPPoE ,
OSPF is now used for management and just wondering if the the original IP's + OSPF network setting were correct ?
Example if a one side of PTP was using IP 192.168.1.13/30 network 192.168.1.12/30 and the other side of the PTP was using IP 192.168.1.14/30 network 192.168.1.12/30
Then we have another devices using network /24 - example IP 192.168.1.100/24 network 192.168.1.0/24
In other words can you have IP combinations of /30 + /29 + /28 + /27 + /26 + /25 along with /24 on a network?
is this a bad configuration setup.
In other words can you have IP combinations of /30 + /29 + /28 + /27 + /26 + /25 along with /24 on a network?
is this a bad configuration setup.
The original configuration was done by a techie who is no longer available and I am trying to educate myself why certain configurations exist on this live network,You only need the network statement once, why are you creating multiple /30 network statements in ospf when you already have it declared with the 1 /8?. MAke sure you summarize routes on area border routers, to prevent flapping
I don't know what you mean they are used for a backup.
You are correct that is not how OSPF is supposed to work! But when a Cisco certified network consultant first adds 10.0.0.0/8 in OSPF network and then proceeds to add /30's within that ip rangeNo that's not how ospf is suppose to works. If your going to go in and enable and disable routes then you need to go back to static routes. Without seeing the big picture that looks to be someone learning how to use ospf. and was making a network statement for every network until they realized they only need to make 1 that summarizes them all.
I understand this but while a 1 /8 could be used on the initial network configuration setup but once the 20 /30 etc have been setup then disable or remove the 1 /8 ,ospf does not care whether you have 20 /30 routes or 1 /8 (or any other mask that summarizes the other ones) They do the same exact thing.
You are correct that is not how OSPF is supposed to work! But when a Cisco certified network consultant first adds 10.0.0.0/8 in OSPF network and then proceeds to add /30's within that ip range
with OSPF interfaces network-type=point-to-point, It had me wondering if this was best network configuration practice! maybe this type of configuration works OK on higher-end equipment but not so good on MIkrotik,
You are correct that is not how OSPF is supposed to work! But when a Cisco certified network consultant first adds 10.0.0.0/8 in OSPF network and then proceeds to add /30's within that ip range
with OSPF interfaces network-type=point-to-point, It had me wondering if this was best network configuration practice! maybe this type of configuration works OK on higher-end equipment but not so good on MIkrotik,
Just to disambiguate a bit, I think you're conflating two different things. But let's talk certification for a minute
As someone pointed out
1) You can be certified and still have no idea what you're doing
2) Certifications are the beginning of network engineering knowledge and are often broad in scope - they are nowhere near definitive
Be careful in using that as the only measure to justify a network design or practice
That said, i'll share my relevant certs if it's helpful - I have a background in both MikroTik and Cisco as I currently hold MIkroTik's MTCINE expert internetworking certification and have been Cisco certified since 2003 - currently i'm an active Cisco CCNP ENT (converted from R&S)
Now for the difference between OSPF config and subnetting.
OSPF network statement configuration allows for the configuration of different mask lengths so that you can be more or less specific about which interfaces participate in OSPF and start exchanging hellos. It does not have any bearing on the subnet configured for an interface. You can specify a /32 length in OSPF for an interface that is configured as a /27 if you don't want any other interface within a /24 that covers the /27 to be active in OSPF.
Conversely, you can be more permissive and configure a network statement as a /24 so that any /27 inside that range will automatically start sending hellos and participate in OSPF. It's worth noting that the "network" style of OSPF config is older and most operating systems have been moving to interface level config for more than 10 years.
Now, to the point about subnet overlap in addressing - generally it's not a good idea to configure overlapping subnets as it creates confusion and not all operating systems support this practice without the use of VRFs. A notable exception is during a network migration, if overlapping subnets exist between two different networks or multiple devices are being combined into a single device and that creates subnet overlap, sometimes it's helpful to have that capability and live with the overlap for a short while until the network can be renumbered.
It's also worth noting this is one of the great strengths of IPv6 - as a general rule, subnet overlap isn't possible except in special ranges like doc prefixes or ULA.
Thank you also for taking the time to give a very informative reply, however this raises two questions......
1) You can be certified and still have no idea what you're doing
2) Certifications are the beginning of network engineering knowledge and are often broad in scope - they are nowhere near definitive
Be careful in using that as the only measure to justify a network design or practice
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