There has been enough confusion regarding arp responders in
ovn to warrant some additional comments; hence add a
general description regarding why they exist and document
the special cases.
The patch goes along with patch fix for vtep ports here:
https://patchwork.ozlabs.org/patch/675796/
Signed-off-by: Darrell Ball <dlu998 at gmail.com>
---
ovn/northd/ovn-northd.8.xml | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/ovn/northd/ovn-northd.8.xml b/ovn/northd/ovn-northd.8.xml
index 307e8be..0755213 100644
--- a/ovn/northd/ovn-northd.8.xml
+++ b/ovn/northd/ovn-northd.8.xml
@@ -415,14 +415,29 @@
<h3>Ingress Table 9: ARP/ND responder</h3>
<p>
- This table implements ARP/ND responder for known IPs. It contains these
- logical flows:
+ This table implements ARP/ND responder for known IPs. The advantage
+ of the arp responder flow is to limit arp broadcasts by locally
+ responding to arp requests without the need to send to other
+ hypervisors. One common case is when the inport is a logical
+ port associated with a VIF and the broadcast is responded to on the
+ local hypervisor rather than broadcast across the whole network and
+ responded to by the destination VM. It contains these logical flows:
</p>
<ul>
<li>
Priority-100 flows to skip ARP responder if inport is of type
- <code>localnet</code>, and advances directly to the next table.
+ <code>localnet</code> or <code>vtep</code>, and advances directly
+ to the next table. These port types are skipped because the arp
+ requests are received by multiple hypervisors which all have the
+ same mac binding locally. There are some special cases:
+ north->south traffic using the l2gateway port will use an arp
+ responder on the l2 gateway chassis in the context of a logical
+ switch datapath. Another case is when traffic flows from
+ south->north or east->west and goes through the gateway router.
+ This arp request will flow through a transit logical switch at
+ the destination hypervisor before going through the gateway router
+ and its inport will be a logical switch router type port.
</li>
<li>
--
1.9.1