Default Gateway for a system v/s Default gateway per Interface
Johnathan Mantey
johnathanx.mantey at intel.com
Sat May 9 03:42:50 AEST 2020
Ratan,
Thanks for clarifying.
On 5/7/20 11:35 PM, Ratan Gupta wrote:
>
> Jonathan,
>
>
> On 5/4/20 9:44 PM, Johnathan Mantey wrote:
>> Ratan,
>>
>> We're not using Windows. What is the Linux kernel/systemd going to do
>> for the Metric? So far the only value that has been applied to the
>> Metric is "0" (assigned by ??).
> I was trying to explain your query "What does it mean to "use the
> default metric"?" I am hoping the Idea would be same to understand the
> behavior of default metric value.
> In OpenBmc systemd assigns the default metric value for static
> routes/DHCP routes(if the DHCP server is not providing the metric value)
>
> Default Metric means what systemd-networkd assigns if the metric is
> not given by the user(in case of static)/DHCP server. Static Routes
> gets added as default metric value as 0 by systemd-networkd.
>> As the Microsoft article points out, using a low value Metric for
>> "private" nets is to be avoided.
>> Our DHCP servers are supplying a Metric value of 1024. I'm sure other
>> network managers use different values.
>
> I am hoping that this behavior in your case is coming through
> systemd-netwokd, I also observed this.
> https://github.com/systemd/systemd/blob/c51c6f2f574e8c107994057c13a6506d93966a23/src/network/networkd-dhcp-common.h#L8
>
>> I don't know how to solve this issue. Especially for the IPMI use
>> case of assigning a static address. IPMI doesn't have the ability to
>> assign metric values. At least with Redfish we can have that feature
>> added.
> As I mentioned before that we can come up with route management
> feature where user can add/delete/update route(i.e) user can change
> the metric value also for a route.
>>
>> On 5/4/20 6:38 AM, Ratan Gupta wrote:
>>>
>>>
>>> On 4/29/20 12:19 AM, Johnathan Mantey wrote:
>>>> I think I understand most of your plan.
>>>>
>>>> What does it mean to "use the default metric"?
>>>
>>> https://support.microsoft.com/en-in/help/299540/an-explanation-of-the-automatic-metric-feature-for-ipv4-routes
>>>
>>> Instead of user level application assigns the metric value, Let the
>>> kernel decide which gateway should be used.
>>>
>>> I understand that there should be a way through which we should be
>>> able to change the metric value but that can be implemented later
>>> with some thing like route management where user should be able to
>>> add HostRoutes/Network routes etc, chnaging the values of the routes
>>> etc.
>>>
>>>>
>>>> On 4/28/20 8:16 AM, Ratan Gupta wrote:
>>>>>
>>>>> Hi Jonathan,
>>>>>
>>>>> On 4/28/20 1:00 AM, Johnathan Mantey wrote:
>>>>>> Ratan,
>>>>>>
>>>>>> Can you provide more info about how you plan to implement this?
>>>>> I am not getting, Do you mean to say how to get the per interface
>>>>> gateway from system? that would be through netlink, and during
>>>>> configuration we would use the systemd-networkd file configuration.
>>>>>>
>>>>>> The Redfish schemas already have a per IP addr Gateway entry,
>>>>>> which OBMC is ignoring. Is it better to modify the existing D-Bus
>>>>>> schema (i.e. versioning discussion), or just use what is
>>>>>> presently in existence?
>>>>> Redfish schema are getting changed to accommodate this through the
>>>>> following issue https://github.com/DMTF/Redfish/issues/3609.
>>>>>
>>>>> The above issue(gateway/interface) exist only for the IPv4 redfish
>>>>> schema, IPv6 redfish is already having default gateway per interface
>>>>>
>>>>> http://redfish.dmtf.org/schemas/v1/EthernetInterface.v1_5_1.json#/definitions/EthernetInterface
>>>>>
>>>>>>
>>>>>> That said, doing as you propose melds better with how IPMI (i.e
>>>>>> Set LAN Configuration Parameter 12) works.
>>>>>>
>>>>>> As Patrick pointed out, there's no IPMI or Redfish control over
>>>>>> the routing metric parameter. What are your thoughts on how to
>>>>>> reconcile applying a metric value?
>>>>> We will go with default metric value as today as underlying stack
>>>>> tries for fallback gateway.
>>>>>> I've long been desirous of getting Williams submission merged:
>>>>>> https://gerrit.openbmc-project.xyz/c/openbmc/phosphor-networkd/+/20799
>>>>>> as it can be used to improve the collection of netlink stats.
>>>>>>
>>>>>> Redfish exacerbates this whole problem by allowing a collection
>>>>>> of static IP addresses (and a DHCP addr) per NIC, unlike IPMI
>>>>>> which was very one to one with IP addr/NIC.
>>>>>>
>>>>>> Thanks for investigating this and working to implement a solution.
>>>>>>
>>>>>> On 4/27/20 4:11 AM, Ratan Gupta wrote:
>>>>>>>
>>>>>>> Thanks Patrick, William for sharing the feedbacks
>>>>>>>
>>>>>>> I will start working on the changes.
>>>>>>>
>>>>>>>
>>>>>>> On 4/24/20 11:15 PM, William Kennington wrote:
>>>>>>>> Sounds good to me, we have needed this for a long time because
>>>>>>>> the current gateway configuration breaks our v6 stack with
>>>>>>>> multiple NICs.
>>>>>>>>
>>>>>>>> On Fri, Apr 24, 2020 at 8:21 AM Patrick Williams
>>>>>>>> <patrick at stwcx.xyz <mailto:patrick at stwcx.xyz>> wrote:
>>>>>>>>
>>>>>>>> On Fri, Apr 24, 2020 at 08:36:26PM +0530, Ratan Gupta wrote:
>>>>>>>> > ~~~~~~~~~~~~~
>>>>>>>> > Kernel IP routing table
>>>>>>>> > Destination Gateway Genmask Flags
>>>>>>>> MSS Window irtt
>>>>>>>> > Iface
>>>>>>>> > 0.0.0.0 19.168.2.1 0.0.0.0 UG
>>>>>>>> 0 0 0
>>>>>>>> > eth0
>>>>>>>> > 0.0.0.0 10.10.10.1 0.0.0.0 UG
>>>>>>>> 0 0 0
>>>>>>>> > eth1
>>>>>>>> > ~~~~~~~~~~~~~~
>>>>>>>> >
>>>>>>>> > Kernel will first try using the default gateway having
>>>>>>>> higher metric
>>>>>>>> > value and then fall back to the lower.
>>>>>>>>
>>>>>>>> I'm not seeing us with an interface to adjust the metric for an
>>>>>>>> interface. I think we need to add that at the same time?
>>>>>>>>
>>>>>>> Not now, As per my testing if metric value is not defined and
>>>>>>> both the routes
>>>>>>>
>>>>>>> having same metric then kernel tries one after other. We can
>>>>>>> bring the metric
>>>>>>>
>>>>>>> later.
>>>>>>>
>>>>>>>> Otherwise, I
>>>>>>>> don't think we have a way to specify which interface
>>>>>>>> outside-the-subnet
>>>>>>>> should go (vs today we can set the default-gateway to the
>>>>>>>> desired
>>>>>>>> interface's gateway).
>>>>>>>> --
>>>>>>>> Patrick Williams
>>>>>>>>
>>>>>>
>>>>>> --
>>>>>> Johnathan Mantey
>>>>>> Senior Software Engineer
>>>>>> *azad te**chnology partners*
>>>>>> Contributing to Technology Innovation since 1992
>>>>>> Phone: (503) 712-6764
>>>>>> Email: johnathanx.mantey at intel.com
>>>>>> <mailto:johnathanx.mantey at intel.com>
>>>>>
>>>>> Ratan
>>>>>
>>>>
>>>> --
>>>> Johnathan Mantey
>>>> Senior Software Engineer
>>>> *azad te**chnology partners*
>>>> Contributing to Technology Innovation since 1992
>>>> Phone: (503) 712-6764
>>>> Email: johnathanx.mantey at intel.com <mailto:johnathanx.mantey at intel.com>
>>>>
>>
>> --
>> Johnathan Mantey
>> Senior Software Engineer
>> *azad te**chnology partners*
>> Contributing to Technology Innovation since 1992
>> Phone: (503) 712-6764
>> Email: johnathanx.mantey at intel.com <mailto:johnathanx.mantey at intel.com>
>>
--
Johnathan Mantey
Senior Software Engineer
*azad te**chnology partners*
Contributing to Technology Innovation since 1992
Phone: (503) 712-6764
Email: johnathanx.mantey at intel.com <mailto:johnathanx.mantey at intel.com>
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