Latest questions from the community.
The poster spent two days trying to bring up a single-mode fiber link between an older Arista switch and a Cisco Catalyst 3650 (IOS-XE 3.7.5) with Cisco GLC-LH-SMD (SFP-LH-SMD) optics; the path runs through five patch cords in the same building and had been tested by the cabling contractor. At…
The poster, a new owner of a Cisco Nexus 93180YC-EX running NX-OS 7.0(3)I4(7), cannot bring up any 25G link. ipolex SFP28 DAC cables are recognized ('type is SFP-H25GB-CU1M', 'name is OEM', 'part number is SFP-H25G-CU1M', 'nominal bitrate is 25500 MBit/sec', 'DOM is not supported') but the port…
The poster runs temporary event networks and has twice hit heavy frame errors on 10G links between MikroTik and Cisco switches. About a year earlier a Cisco Catalyst 2960-S with 10G uplinks connected to a MikroTik CRS317-1G-16S+ showed CRC errors on the Cisco side and swapping cables did not help…
On a Cisco Nexus N9K-C93180YC-FX, QSFP-40G-SR-BD BiDi modules are not detected at all: nothing appears in the logs when they are inserted and they are absent from 'show interface transceiver', whereas QSFP-40GE-LR4 modules in the same ports are logged and listed normally. Several QSFP-40G-SR-BD…
The poster asked whether a 10G SFP+ SR or LR optic in one switch can auto-negotiate down to 1G to link over fiber with a 1G SFP in another switch, and if not, how to attach a handful of 1G optical connections from a 1G switch to a 10G switch. They understood that Cisco SFP+ optics run only at 10G…
In the poster's data center several Cisco CWDM SFP/GBIC links stopped working: some ports went err-disabled (one with link-flap as the cause) and others simply showed notconnect. Troubleshooting included shut/no shut, reseating the modules, moving the CWDM SFPs to other ports, replacing the patch…
The poster wanted to use a 40G QSFP+ to 4x10G SFP+ DAC breakout cable on a Cisco Catalyst 9500-32QC-E running IOS XE 17.6.4 (Bengaluru). The 'hw-module breakout' command is rejected; in global configuration only 'hw-module slot' and 'hw-module subslot' are offered. The switch is not running…
The poster could not find Cisco documentation describing how to set the frequency or ITU channel of a DWDM-SFP10G-C tunable 10G SFP+. A follow-up question asked whether a CPAK-100G-LR4 in a CRS-X 4-port 100GE LAN/OTN card could be tuned to a wavelength and connected directly to a ROADM of an…
A Cisco Catalyst 3850-24XS with an SFP-10G-LR (1310 nm) connects over a single-mode cross-connect to a Tier-1 carrier's layer-2 DWDM equipment in the same data center. When the carrier shuts the circuit down, TenGigabitEthernet2/0/23 goes 'down, line protocol is down (notconnect)' yet 'show…
Two Cisco Catalyst 3750-X switches (WS-C3750X-24P-L and WS-C3750X-48P-L) run identical code. A Cisco GLC-SX-MMD is detected normally in Gi1/1/1 of the first switch, but the second switch reports 'media type is Not Present' with 'link type is force-up' on Gi1/1/1, and 'show idprom interface Gi…
The poster (in a machine-translated post from the Spanish-language community) tried to connect two Cisco Business CBS350-24T-4X switches through their SFP+ ports using MikroTik XS+2733LC15D modules. No connectivity is established and the ports end up blocked by the switch's Link Flap Prevention…
The poster planned to install an Intel X520 adapter (Cisco PID N2XX-AIPCI01) into a Cisco UCS C240 server and use Cisco SFP-10G-SR or SFP-10G-LR transceivers, and asked whether the combination has compatibility problems. A later reader asked whether the Cisco SFP-H10GB-CU3M= twinax cable would work…
A friend of the poster bought several GLC-T copper SFPs sold as original Cisco, but their serial numbers had an unfamiliar format (00000MTC1719055H, 00000MTC171903XL and similar). 'show interface ethernet 1/45 transceiver sprom' on a Cisco Nexus 5596 lists the module as SFP-1000BASE-T, vendor name…
The poster connected a Dell server to a Cisco Catalyst C9500-48Y4C (IOS XE 17.9.3) using a Dell L56SF018-SD-R 3 m DAC (DAC-SFP-3M). The cable is not in Cisco's optics compatibility matrix, and 'show interface status' shows port TwentyFiveGigE1/0/35 as err-disabled. Logging shows…
The poster asked why third-party SFP modules stopped working after upgrading Cisco switches to IOS 15.2, whereas other vendors accept Cisco or other optics, and whether this is a technical limitation. No model, log output or interface details were given despite requests. In a later update the…