Re: [Nagios-devel] Improving the host logic
Posted: Thu Dec 15, 2005 4:32 am
Shane Stixrud wrote:
> On Wed, 14 Dec 2005, Andreas Ericsson wrote:
>
>>
>> Layer 2 devices can be parents just as well as layer 3 devices, with
>> any level of redundancy anywhere you want.
>
>
> Sure you can define layer 2 devices as parents of a child device, but so
> what?? If you are using the parent definition for layer 2 it cannot
> also be used for layer 3 parents (for that same device) without
> unexpected behavior as far as I can tell.
>
Yes it can, although the layer 3 node becomes the parent of the layer 2
node which is the Right Thing to do.
>>> The existing parent logic should be able to remain pretty much as is,
>>> merely renaming the directive to "l3parents" to distinguish this
>>> should only be used for layer 3 parents.
>>>
>>
>> But it shouldn't. Each electron that makes up a part of a packet has
>> to traverse a chain of physical nodes to reach its destination. Each
>> of those nodes is a parent to whatever node they send the electrons on
>> to next.
>
>
> Sure, there is a physical chain, however nagios does not monitor each
> electron as it transfers over that chain, rather it contacts the IP
> addresses of each device along that chain to determine which link in
> that chain may be broken.
>
Oh, now I understand what you're talking about. You're still wrong though.
The only difference (packet-wise) between a layer 2 device and a layer 3
device is that the layer 3 device modifies the TTL of the packets it
sends on. It has to do this whenever it sends a packet to a new subnet
(read RFC 791 for more info). Thus, when home users access their
internal network over their multi-port router the TTL won't be
decremented. When they access the outside world it will be.
Nagios is supremely indifferent to this distinction. This is good
because it can support any type of network equipment.
>>
>>
>>> Duplicating the existing parents logic and assigning it a new name
>>> called l2parents. Nagios would then need to be modified to first check
>>> l2parents before proceeding to the l3parents when a device goes into
>>> a NON-OK state. If all l2 parents or l3 parents are down nagios
>>> would follow the l2 or l3 inherited parents just as it does today.
>>>
>>
>> Gaining what? Here's how we set up it. Mindscale to any level and
>> depth you like. I've never seen nagios do anything but The Right Thing
>> with config like this.
>>
> [snip]
>
> Sure this works fine when the switch is isolated to one layer 3 network
> (i.e. no vlans). Care to share the magic tricks you use to tie vlan
> assigned switch ports to the correct layer3 devices/interfaces??
Sure. Give the switch an IP in each network and make it switch2-vlan23
or, if the route goes through the same physical devices no matter the
VLAN, use whatever IP you already have on it. Obviously, this doesn't
work if you can't set an IP on the switch and it can't respond to ICMP
or some such (in which case you almost certainly won't have VLAN's on them).
> As far
> as I can tell if my switch hosts 20 vlans I can either set its parent to
> one of those vlans or all of them. If I do 1 then I have a 1 in 20
> chance of suppressing notifications, if I do all fo them then every vlan
> would have to fail for it to suppress notifications. I am willing to be
> wrong here, please show me the error in my thinking.
>
You're thinking "one device, one host" when you should be thinking "one
IP, one host" (this is btw also what I was referring to in the acidity
concluding my last email on this topic). You can add the same physical
device as a separate host a million times if you want to. If you have
VLAN's this is almost always the right thing to do because you will then
notice when one VLAN is incorrectly configured.
>
>>
>>> IMO this change would be the least intrusive, adds layer2 parent
>>> support and allows for redundancy detection for both layer2 and
>>> layer3 devices with little added complexity.
>>>
>>
>> If you're going to add all layer 2 devices in their own parenting link
>> you need to know when layer 3 devices pop in between them
>
>
> Each host defini
...[email truncated]...
This post was automatically imported from historical nagios-devel mailing list archives
Original poster: [email protected]
> On Wed, 14 Dec 2005, Andreas Ericsson wrote:
>
>>
>> Layer 2 devices can be parents just as well as layer 3 devices, with
>> any level of redundancy anywhere you want.
>
>
> Sure you can define layer 2 devices as parents of a child device, but so
> what?? If you are using the parent definition for layer 2 it cannot
> also be used for layer 3 parents (for that same device) without
> unexpected behavior as far as I can tell.
>
Yes it can, although the layer 3 node becomes the parent of the layer 2
node which is the Right Thing to do.
>>> The existing parent logic should be able to remain pretty much as is,
>>> merely renaming the directive to "l3parents" to distinguish this
>>> should only be used for layer 3 parents.
>>>
>>
>> But it shouldn't. Each electron that makes up a part of a packet has
>> to traverse a chain of physical nodes to reach its destination. Each
>> of those nodes is a parent to whatever node they send the electrons on
>> to next.
>
>
> Sure, there is a physical chain, however nagios does not monitor each
> electron as it transfers over that chain, rather it contacts the IP
> addresses of each device along that chain to determine which link in
> that chain may be broken.
>
Oh, now I understand what you're talking about. You're still wrong though.
The only difference (packet-wise) between a layer 2 device and a layer 3
device is that the layer 3 device modifies the TTL of the packets it
sends on. It has to do this whenever it sends a packet to a new subnet
(read RFC 791 for more info). Thus, when home users access their
internal network over their multi-port router the TTL won't be
decremented. When they access the outside world it will be.
Nagios is supremely indifferent to this distinction. This is good
because it can support any type of network equipment.
>>
>>
>>> Duplicating the existing parents logic and assigning it a new name
>>> called l2parents. Nagios would then need to be modified to first check
>>> l2parents before proceeding to the l3parents when a device goes into
>>> a NON-OK state. If all l2 parents or l3 parents are down nagios
>>> would follow the l2 or l3 inherited parents just as it does today.
>>>
>>
>> Gaining what? Here's how we set up it. Mindscale to any level and
>> depth you like. I've never seen nagios do anything but The Right Thing
>> with config like this.
>>
> [snip]
>
> Sure this works fine when the switch is isolated to one layer 3 network
> (i.e. no vlans). Care to share the magic tricks you use to tie vlan
> assigned switch ports to the correct layer3 devices/interfaces??
Sure. Give the switch an IP in each network and make it switch2-vlan23
or, if the route goes through the same physical devices no matter the
VLAN, use whatever IP you already have on it. Obviously, this doesn't
work if you can't set an IP on the switch and it can't respond to ICMP
or some such (in which case you almost certainly won't have VLAN's on them).
> As far
> as I can tell if my switch hosts 20 vlans I can either set its parent to
> one of those vlans or all of them. If I do 1 then I have a 1 in 20
> chance of suppressing notifications, if I do all fo them then every vlan
> would have to fail for it to suppress notifications. I am willing to be
> wrong here, please show me the error in my thinking.
>
You're thinking "one device, one host" when you should be thinking "one
IP, one host" (this is btw also what I was referring to in the acidity
concluding my last email on this topic). You can add the same physical
device as a separate host a million times if you want to. If you have
VLAN's this is almost always the right thing to do because you will then
notice when one VLAN is incorrectly configured.
>
>>
>>> IMO this change would be the least intrusive, adds layer2 parent
>>> support and allows for redundancy detection for both layer2 and
>>> layer3 devices with little added complexity.
>>>
>>
>> If you're going to add all layer 2 devices in their own parenting link
>> you need to know when layer 3 devices pop in between them
>
>
> Each host defini
...[email truncated]...
This post was automatically imported from historical nagios-devel mailing list archives
Original poster: [email protected]