topic Fabric Extend via L3 MTU Issue in ExtremeSwitching (Other) https://community.extremenetworks.com/t5/extremeswitching-other/fabric-extend-via-l3-mtu-issue/m-p/12519#M3547 I will apologize in advance if there is a better community for this question, I guessed as to where it could go.<BR /><BR /><SPAN style="text-decoration: underline; color: #333333;">Background</SPAN><BR /><BR /> <UL> <LI>We have a number of locations which we have extended our Fabric. <UL> <LI>21 locations that connect to our CORE via a subscribed L3 service.&nbsp; <UL> <LI>The service handles routes to each node by static route definition.</LI> <LI>The service has a subscribed MTU of 3900.</LI> </UL> </LI> <LI>4 locations that connect to our CORE via dark fiber or a shared L2 service (METRO) where the VLAN ids are unique to the fiber use partners.</LI> </UL> </LI> <LI>We've extended the fabric from our CORE (VSP7400s) to each of the locations which can be a VSP4900 or XA14800 depending on that location. <UL> <LI>All system MTUs are 1950.</LI> </UL> </LI> <LI>ISIS Adjacencies are up.</LI> <LI>ISIS LSDB shows all locations.</LI> <LI>ISIS SPBM I-SID shows all currently active C-VLANs with I-SIDs.</LI> <LI>L2 VSN traffic works with the conditions described below.</LI> </UL> <P><BR /><SPAN style="text-decoration: underline;">Issue Description</SPAN></P> <UL> <LI>L2 VSNs between dark fiber/L2 service connected locations <EM>have no issue with any flows</EM>.</LI> <LI>L2 VSNs between the L3 subscribed service connected locations have no issue as long as the <EM>MTU doesn't exceed a given value</EM>.&nbsp; <UL> <LI>Example: <UL> <LI>(Windows 10 System) <UL> <LI>[WORKS] ping A.B.C.D -l 1470&nbsp;</LI> <LI>[FAILS] ping A.B.C.D -l 1741</LI> </UL> </LI> </UL> </LI> </UL> </LI> </UL> <SPAN style="text-decoration: underline;">Troubleshooting<BR /></SPAN><BR /> <UL> <LI>Verified MTU settings between L3 subscribed service connected locations: <UL> <LI>(Windows 10 System) <UL> <LI>[WORKS] ping A.B.C.D -l 1472 -f <UL> <LI>A.B.C.D is a non-fabric endpoint reached via L3 subscribed service.</LI> </UL> </LI> </UL> </LI> </UL> </LI> <LI>Removed 2 devices reachable via the L3 subscribed service from our main fabric and created a new one between those devices themselves. <UL> <LI>Used multiple incrementing values per test for command on both sides of fabric: <UL> <LI>logical-intf isis 1 dest-ip A.B.C.D mtu ABCD <UL> <LI>ABCD --&gt; 1950, 2000, 2050</LI> </UL> </LI> </UL> </LI> <LI>Same results.</LI> </UL> </LI> <LI>Changed the fabric endpoints to both be XA1480s and recreated a fabric between them. <UL> <LI>Same results.</LI> </UL> </LI> </UL> <SPAN style="text-decoration: underline;">Question</SPAN><BR /><BR />Can someone recommend some testing or have ideas on how to solve this issue?&nbsp;<BR /><BR />Thank you in advance. Mon, 08 Nov 2021 19:03:00 GMT RobertB 2021-11-08T19:03:00Z Fabric Extend via L3 MTU Issue https://community.extremenetworks.com/t5/extremeswitching-other/fabric-extend-via-l3-mtu-issue/m-p/12519#M3547 I will apologize in advance if there is a better community for this question, I guessed as to where it could go.<BR /><BR /><SPAN style="text-decoration: underline; color: #333333;">Background</SPAN><BR /><BR /> <UL> <LI>We have a number of locations which we have extended our Fabric. <UL> <LI>21 locations that connect to our CORE via a subscribed L3 service.&nbsp; <UL> <LI>The service handles routes to each node by static route definition.</LI> <LI>The service has a subscribed MTU of 3900.</LI> </UL> </LI> <LI>4 locations that connect to our CORE via dark fiber or a shared L2 service (METRO) where the VLAN ids are unique to the fiber use partners.</LI> </UL> </LI> <LI>We've extended the fabric from our CORE (VSP7400s) to each of the locations which can be a VSP4900 or XA14800 depending on that location. <UL> <LI>All system MTUs are 1950.</LI> </UL> </LI> <LI>ISIS Adjacencies are up.</LI> <LI>ISIS LSDB shows all locations.</LI> <LI>ISIS SPBM I-SID shows all currently active C-VLANs with I-SIDs.</LI> <LI>L2 VSN traffic works with the conditions described below.</LI> </UL> <P><BR /><SPAN style="text-decoration: underline;">Issue Description</SPAN></P> <UL> <LI>L2 VSNs between dark fiber/L2 service connected locations <EM>have no issue with any flows</EM>.</LI> <LI>L2 VSNs between the L3 subscribed service connected locations have no issue as long as the <EM>MTU doesn't exceed a given value</EM>.&nbsp; <UL> <LI>Example: <UL> <LI>(Windows 10 System) <UL> <LI>[WORKS] ping A.B.C.D -l 1470&nbsp;</LI> <LI>[FAILS] ping A.B.C.D -l 1741</LI> </UL> </LI> </UL> </LI> </UL> </LI> </UL> <SPAN style="text-decoration: underline;">Troubleshooting<BR /></SPAN><BR /> <UL> <LI>Verified MTU settings between L3 subscribed service connected locations: <UL> <LI>(Windows 10 System) <UL> <LI>[WORKS] ping A.B.C.D -l 1472 -f <UL> <LI>A.B.C.D is a non-fabric endpoint reached via L3 subscribed service.</LI> </UL> </LI> </UL> </LI> </UL> </LI> <LI>Removed 2 devices reachable via the L3 subscribed service from our main fabric and created a new one between those devices themselves. <UL> <LI>Used multiple incrementing values per test for command on both sides of fabric: <UL> <LI>logical-intf isis 1 dest-ip A.B.C.D mtu ABCD <UL> <LI>ABCD --&gt; 1950, 2000, 2050</LI> </UL> </LI> </UL> </LI> <LI>Same results.</LI> </UL> </LI> <LI>Changed the fabric endpoints to both be XA1480s and recreated a fabric between them. <UL> <LI>Same results.</LI> </UL> </LI> </UL> <SPAN style="text-decoration: underline;">Question</SPAN><BR /><BR />Can someone recommend some testing or have ideas on how to solve this issue?&nbsp;<BR /><BR />Thank you in advance. Mon, 08 Nov 2021 19:03:00 GMT https://community.extremenetworks.com/t5/extremeswitching-other/fabric-extend-via-l3-mtu-issue/m-p/12519#M3547 RobertB 2021-11-08T19:03:00Z