I've worked on a network upgrading from Netgear M4100 to M4300 switches, with the intent to upgrade from 1000BASE-SX SFP modules to 10GBASE-SR SFP+ modules in a second step since the M4300 are SFP\/SFP+ slots.<\/p>\n
All (that is most) links initially were left at 1G using the SFP modules from the M4100 until we'd swap them out for to SFP+ modules. However even after the fact the remained at 1G even though we previously tested if the old fibers would still support 10GBASE-SR.)<\/p>\n
However even after changing to 10GBASE-SR modules most links remained on 1G speed:<\/p>\n
(m4300) #show fiber-ports optics-info 1\/0\/5\n\n Link Link Nominal\n Length Length Bit Possible\n 50um 62.5um Rate Speed\nPort Vendor Name [m] [m] Serial Number Part Number [Mbps] Rev Compliance Supported Detected\n-------- ---------------- ------ ------ ---------------- ---------------- ------- ---- ---------------- ------------ ---------\n1\/0\/5 FS 30 15 XXXXXXXXXXXX SFP-10GSR-85 10300 10GBase-SR Yes 1G\n\n(m4300) #show interfaces status 1\/0\/5\n\n Link Physical Physical Media Flow Control\nPort Name State Mode Status Type Status\n--------- ---------------------------- ------ ---------- ---------- ------------------ ------------\n1\/0\/5 Up Auto 1000 Full 10GBase-SR Inactive<\/code><\/pre>\nLesson learned: 10GBASE-SR modules can be dual-rate<\/h3>\n
Although I knew many old 2G modules for FiberChannel supported 1G ethernet I didn't knew that at least some 10GBASE-SR modules would also be dual-rate.<\/p>\n
On the positive side one can swap out SFP for SFP+ modules on one end of a link, wait for the other end and still get a working connection albeit at 1G before swapping the module on the other end.<\/p>\n
Finding the cause and a fix<\/h3>\n
Shutting down the port and removing \/ re-inserting the SFP modules on both ends didn't make any difference.<\/p>\n
However it dawned on me when I compared a port configuraton "stuck" on 1G against an empty (default) configration:<\/p>\n
(m4300) #show running-config interface 1\/0\/5\n\n!Current Configuration:\n!\ninterface 1\/0\/5\nauto-negotiate\nspeed auto 1000 full-duplex\n[...]\nexit<\/code><\/pre>\nThe default (empty) config of unused ports didn't have these lines and didn't appear on the links that were newly installed and thus at 10G.<\/p>\n
What eventually fixed the "negotiated" speed was:<\/p>\n
configure\ninterface 1\/0\/5\nno auto-negotiate\nspeed auto 10G full-duplex\nexit<\/code><\/pre>\nIf both ends are M4300's this needs to be "undone" on both sides of the link. <\/p>\n
Afterwards the link came back up at 10G and both config lines disappeared from the running-config. This indicates that "no auto-negotiate" and "speed 10G full-duplex" were in fact the default config.<\/p>\n
Why did this even happen?<\/h3>\n
I wanted to know what caused this to even happen so I tried to reproduce the situation:<\/p>\n
\n- It was definitely not a human being, that I was pretty certain, it was not documented in the configuration docs.<\/li>\n
- Simply inserting a 1000BASE-SX module in an SFP+ slot wouldn't add the 2 lines.<\/li>\n
- Connecting and successfully bringing up the link on 1G however did. <\/li>\n<\/ul>\n
The 2 lines remain even after removing the SFP module and eventually upgrading to SFP+.<\/p>\n
Conclusion<\/h3>\n
If you upgrade from 1G to 10G on M4300 while using the same SFP+ slot, don't forget to undo the auto-added auto-negotiate and speed lines to get full speed on the SFP+ slots.<\/p>\n","protected":false},"excerpt":{"rendered":"
I’ve worked on a network upgrading from Netgear M4100 to M4300 switches, with the intent to upgrade from 1000BASE-SX SFP modules to 10GBASE-SR SFP+ modules in a second step since the M4300 are SFP\/SFP+ slots. All (that is most) links initially were left at 1G using the SFP modules from the M4100 until we’d swap … more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_crdt_document":"","footnotes":""},"categories":[1],"tags":[69,66,30,67,68],"class_list":["post-628","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-l2","tag-m4300","tag-netgear","tag-sfp","tag-switching"],"_links":{"self":[{"href":"https:\/\/www.simweb.ch\/blog\/wp-json\/wp\/v2\/posts\/628","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.simweb.ch\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.simweb.ch\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.simweb.ch\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.simweb.ch\/blog\/wp-json\/wp\/v2\/comments?post=628"}],"version-history":[{"count":0,"href":"https:\/\/www.simweb.ch\/blog\/wp-json\/wp\/v2\/posts\/628\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.simweb.ch\/blog\/wp-json\/wp\/v2\/media?parent=628"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.simweb.ch\/blog\/wp-json\/wp\/v2\/categories?post=628"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.simweb.ch\/blog\/wp-json\/wp\/v2\/tags?post=628"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}